So, time for some analysis of Mami: (warning: long post)
You sneak up on Mami. Her bench is shared with Kazumi, Umika, and Kaoru, but that's fine. That's enough room for you to sneak up on her, covering her eyes from behind and pressing a gentle kiss to the top of her head.
"Hi," you breathe. "Guess who?"
"Sabrina," Mami breathes, melting back against you. You can feel the tightly corded tension in her body softening as you shift to hug her properly, arms around her waist. She leans her head against your collarbone, eyes sliding shut with a contented sigh.
"Hey, Mami," you whisper. "How are you?"
"Better now," she murmurs, eyes fluttering open to stare at you.
"Did you have fun?" you ask, addressing the question to Kazumi and her friends as much as you do Mami.
"It- it was good to catch up," Mami agrees.
...
Mami bumps her shoulder against you, a warm smile on her lips, and you squeeze her hand lightly. There's a touch of strain around her eyes, but it's ebbing fast.
There are two main points to glean from this, but in order to get to them, I need to provide some context:
Mami obviously has severe abandonment issues, but it doesn't merely end there. She was also incredibly
lonely during those times, and increasingly
afraid of
being abandoned and being alone, the more it kept happening. This would also have an effect on her self-confidence and self-esteem. Again, nothing groundbreaking here. However, it's important to keep in mind that these circumstances would lead to her living in a state of almost constant emotional pain, or at least discomfort. She did her best to ignore it, to distract herself from it, and she had some success, but it was always there.
Then comes Sabrina. At first, Sabrina is a new friend, a new student. There's the initial novelty of Sabrina living with Mami, which she undoubtedly enjoyed greatly (it meant more frequent contact, and it also meant that her home no longer felt 'empty' or a place to remind her of her loneliness). However, Sabrina quickly became much more than that. Sabrina somehow immediately picked up on Mami's loneliness, telling her that she wasn't alone anymore. Then she picked up on Mami's fear of being left behind or being abandoned, and kept reassuring her that she wouldn't leave. As explicitly laid out in the canon bit from Mami's perspective (written by Firn), Mami was constantly dreading when Sabrina would see under her facade of being a cool, dependable, perfect sempai magical girl and discover the real her: terribly afraid, terribly lonely, thinking herself broken and worthless. That, when Sabrina did see it, she'd leave her.
See, unlike her previous students/friends, Sabrina had no reason to get hung up on the "hunt all Familiars" rule--she could cleanse her own gem at will with no cost. But there were other cases, like Masami, who lived elsewhere (but near enough for them to frequently be in contact) and one day told Mami that she needed her space and just dropped out of contact. Thus, even when Mami does nothing wrong or makes no imposition on others, her students can just up and leave her without explanation or warning. This kind of fear is thus pervasive and irrational, because, from her perspective, it doesn't even need a rational basis for it to still come true.
Sabrina is
so good to her, but at the same time, she keeps endangering herself seemingly recklessly. This simultaneously giving Mami too much hope and too much fear/stress/anxiety causes her to break down in front of Sabrina, admitting her true feelings: that she's terrified of being left behind/abandoned, terrified of being alone/is so lonely, feels like she's broken and worthless, etc. And rather than thinking any less of her, Sabrina comforts her, tells her that she's not leaving, that she thinks Mami is an amazing person who has done incredibly meaningful things for a lot of people, and that she's
not broken.
This is big, for a lot of reasons, but biggest reasons are that A) she's never broken down like this to one of her students/friends before, never revealed her truest feelings and fears, and B) she's never directly confronted her worst fears and had things turn out well.
Things get better for her. But it doesn't last, because then comes the truth about Soul Gems and Kyubey, and
this breaks her. Neither of these things were fears she had had; neither of them were issues she had even considered before. The first one is horrifying, yes. But the second is a sense of betrayal, a sense of compounding loneliness. Now, everything in her life before has taken on a darker, new light. Kyubey was never her friend; he was just using her for his own ends: recruiting more magical girls and turning their souls into rocks (from her eyes). This also comes with a huge sense of guilt, because she essentially facilitated everyone else she recruited being horribly tricked as well. In the past, even when everyone else had left her, Kyubey remained with her. As she said, at her last birthday, Kyubey was the only one there. Thus, her past loneliness becomes even worse retroactively: she was always more alone than she had even realized. But to top it all off, in her distress and anguish, she'd told Sabrina to go away.
But Sabrina doesn't leave, doesn't think any less of Mami, and doesn't complain or give any indication of discomfort with Mami desperately clinging onto her. Everything in her life feels wrong, and she no longer feels sure about anything, including herself. Her worldview has been broken, but Sabrina feels like the one rock-solid, unshakably steady thing she can cling to and rely on.
Sabrina isn't merely a best friend, or someone she loves; she's practically a (to put it in terms that I know will be misinterpreted by some) drug to Mami,
but not in a bad way. Anyone with depression or an anxiety disorder will know what it's like to be without your medication when you need it: a state of strong discomfort or misery, one that's inescapable otherwise. Sabrina is everything Mami ever wanted since contracting: someone who made her not feel lonely or left behind, someone who gave her affection and comfort, someone who she could depend on and trust completely, someone she could spend time with and enjoy, someone who would read her well and assuage her fears and doubts. Sabrina is also something of a source of hope for her: a hope of reconciliation with her past friends/students, of a safeguard against her unwittingly or unknowingly driving her friends away, etc.
So, the two conclusions:
1) When Sabrina is around, her anxiety lowers dramatically, her fears go away (relatively speaking), and the PTSD-like reminders of loneliness and isolation get soothed and shooed away. When Sabrina is around, she can finally
relax and feel comfortable and relatively okay. When Sabrina is around, she doesn't feel like she's slowly coming apart at the seams under the weight of her fears, anxiety, loneliness, trauma, or sadness.
2) When catching up with friends she's not seen or spoken to in a while/long time, her anxiety and fears come back with a vengeance, fueled by traumatic memories. In situations like these, when Sabrina isn't around, she lacks that pillar of stability, comfort, reassurance, and support; she lacks that safeguard against accidentally doing or saying something that might drive them away from her again. Thus, being present when Mami is spending time with friends she's reconnecting with is important and helpful to her. If a future situation like this comes up, we could just give Sayaka a ride to her training session, give the payment to Kyouko/Yuma, and then fly back to Mami, and then fly back to pick Sayaka up when she's done. It was good to be there the first time, but not really necessary in the future.
To emphasize these points, I'll requote from above:
"Hi," you breathe. "Guess who?"
"Sabrina," Mami breathes, melting back against you. You can feel the tightly corded tension in her body softening as you shift to hug her properly, arms around her waist. She leans her head against your collarbone, eyes sliding shut with a contented sigh.
See how much Sabrina's presence bring her
relief? This is more than her usual reaction of reuniting with Sabrina after school each day. She's been tense and worried and self-doubting and anxious the entire time Kazumi, Umika, and Kaoru have been here when we weren't. She's enjoyed catching up with them, but it's hard to really enjoy social interaction when you're constantly afraid and anxious. And it's not like Sabrina was gone for long--maybe 70 minutes? And Madoka, Hitomi, and Homura were there with her. It wasn't just "time without Sabrina", is what I'm saying.
"It- it was good to catch up," Mami agrees.
That hesitation there is key. It
was good to catch up, but it wasn't the purely enjoyable experience it otherwise would have been, because her constant fears/anxiety/self-doubts brought on by catching up with a friend she'd not seen in a long time. That kind of thing will fade the more Mami and Kazumi interact. One major point of progress, probably in the future, is if Mami admits her deepest feelings on the matter to Kazumi--her loneliness, fear of being abandoned/left behind, her self-doubts and low self-esteem, her constant fear of saying or doing the wrong thing and driving her friends away, and her fear that, one day, her friends will just distance themselves from her without warning or explanation. And if Kazumi takes all of that in and reaffirms her relationship with Mami, it will be a major point of progress, with many (but not all, and not completely) of her fears and doubts being addressed directly.
Mami bumps her shoulder against you, a warm smile on her lips, and you squeeze her hand lightly. There's a touch of strain around her eyes, but it's ebbing fast.
In some ways, Sabrina being around Mami has an almost instant effect: the sense that everything will be alright, that she most definitely
isn't alone, that she doesn't need to be constant fear of accidentally saying or doing the wrong thing, that she won't notice the signs in others that something is wrong or that they'll decide to distance themselves from her, etc.
But in other ways, Sabrina needs to actively
be there for things in Mami's life (such as her current experiences) for these things to no longer be as scary or hard to deal with. Like the difference between a young child being alone in the dark, and a young child being with his/her mother in the dark. The latter can, over time, make being alone in the dark less scary, because (among other reasons) having the source of comfort and reassurance during the experience makes it less scary, and thus, less fear and anxiety is associated with the experience itself when thinking about it or confronting it. This makes confronting the experience increasingly less scary, to the point that, eventually, confronting it without that source of comfort and reassurance is manageable.
---
Slightly unrelated, but it's worth pointing out: being in an officially (and publicly acknowledged) relationship with Mami is undoubtedly helpful for her. Officially acknowledging a relationship is a degree of commitment. Publicly acknowledging it is a
public commitment, and people are a lot less likely to go back on their public commitments, especially ones displayed directly in front of friends. That, combined with having solid confirmation on the depth and nature of Sabrina's feelings towards her, does a lot to address her fears that Sabrina will leave her.
Officially being in a relationship also makes the displays of comfort, affection (both physical and verbal/emotional, and both giving and receiving), and dedication less a source of anxiety and uncertainty. She's not going to be afraid that Sabrina will one day stop giving her big hugs in public because she's no longer comfortable with others thinking they're romantically inclined (when, hypothetically, Sabrina
isn't inclined, as Mami feared). Likewise, Mami isn't going to be worried that her
asking for big gestures of affection will drive Sabrina away.
While Mami has had friends and students leave her/abandon her before, she's never had a
girlfriend do that. This reduces fears/anxieties/doubts.
Mami also has tangible things she can point to (for her own psyche) that represent the mutual nature of their relationship, too. Canone Picchio (spelling?) is a technique that only works as a
combination of their magic (amusingly, Mami once noted that true combination attacks between magical girls basically weren't a thing). Sabrina has gone to
her as a source of comfort and reassurance, and this has happened well after Sabrina had gone a while without any such needs. It shows that Sabrina needs her, and she won't leave when she no longer needs that comfort or reassurance (because she didn't leave before, when she didn't need it).
That said, one thing we can do to help reassure her about probably her second-greatest remaining fear regarding Sabrina (the first-greatest being that she's killed) is to tell her (under privacy constructs) that, while we can't yet explain
why we're so confident about this due to it involving secrets that aren't ours to share and would be dangerous for Kyubey to overhear, we can tell her that we have very good reason to believe that we sort of...spontaneously came into existence as a result of a Wish. Thus, there aren't really any past memories for us to one day regain or worry about--and amnesia doesn't fit our situation anyway, and memory manipulation powers seem to be pretty rare in magical girls, too. The "created by a Wish" theory would also explain why our soul seemed strange to Kyubey--people aren't normally spontaneously created by Wishes, after all. Lastly, the Wish clearly isn't compelling us to act against our desires, since nothing of the sort has ever happened. Perhaps someone Wished that there would be someone who could improve the lives of magical girls everywhere one day, and we appeared in Mitakihara because that's where we were needed most, and perhaps where we would be best off starting at--with Mami and Homura and Madoka and Sayaka and Hitomi. Perhaps we were needed to beat Walpurgisnacht and end the threat it represents once and for all--and with all of the meguca refugees coming to the city, Mitakihara could become the core or start of a new movement or organization.
Still, that's for later. For now, Kazumi is really the best of Mami's past students/friends to reconnect with first: Kazumi's unwavering kindness, selflessness, and cheerfulness does a lot to assuage Mami's fears. After all, someone so unreservedly happy and kind would have little reason to suddenly cut ties with you, and the selflessness means that hunting all Familiars was probably never a sticking point for her. Nadia revealing that Kazumi was doing well for herself and had her students naming their attacks showed that she clearly still felt inspired by Mami. Kazumi is also the type to not be put off at all by Mami's insecurities, trauma, fears, etc. Lastly, Mami and Kazumi parted on good terms, separation forced more by the reality of how distantly they lived from one another, rather than it happening over a disagreement, fight, or disillusionment.
