Her gaze being drawn to Mami's ribbon around her waist, her hand coming up to idly feel it--the ribbon tied to her in timestop is representative of Mami being someone she can actually trust, is closely working with, is not breaking down or going insane after being lichbombed/Kyubeybombed, is extremely wary of Kyubey and very friendly towards Homura, and someone she is comfortable with mutually tying her powers to in order to work together more effectively. She's long since lost faith in Mami's reliability and her ability to trust in Mami as a friend and mentor--until this loop, where Mami is once again trustworthy in the face of everything, once again friendly and supportive to her, and once again someone she enjoys working with. And this time, uniquely, they're doing all of that as equals.
Oriko and Kirika, so long classified as either a threat to be ruthlessly eliminated or a nonfactor, are defeated once-enemies and now nominal allies that she doesn't trust and is wary of, but cannot eliminate (and not for lack of ability). It's been easy for Homura to forever treat all Witches and Kyubey as a threat to Madoka and simply eliminate them where convenient or necessary (or treat as an enemy, in Kyubey's case, since she literally can't permanently kill him); O&K were made simple by virtue of treating them just like Witches if they even started to become a threat (by contracting), or leaving them alone otherwise. Now, though, she's stuck in this completely new situation where she's forced to work with two girls she doesn't trust and feels to be a threat to Madoka, but at the same time, she acknowledges that O&K might have been eliminated as a threat without killing them, but she has no way to make sure or clearly draw the line.
And what about Sabrina herself? Someone entirely new after all these loops, probably a result of Madoka's ambiguous wish at the end of the previous loop--someone with unbelievable powers, no background, and no memories before the day they met, but almost encyclopedic information about various things regarding the MG system, immediate threats like WPN, and relevant people to Homura's situation. Someone who seems tailor-made--from Madoka's perspective--to help Homura achieve what she couldn't do after countless attempts and struggles. Someone who acts a lot like Madoka, but with a strong pragmatic streak that Homura can relate to, and without a strong self-sacrificing tendency for Homura to worry about. Someone whose powers let her effectively replicate everything a Witch can do, but with conscious control, and allow her to apply them in ways no Witch ever would--perhaps making her the perfect counter to the two enemies Homura could never properly defeat herself (WPN and the danger of her friends grief-spiraling themselves). And yet, someone who seems to be tied to a new, ominous, unknown, and almost unknowable threat she can't quantify nor defend against? Is Sabrina a liability, or even a potential one? Even if she is as a result of this new threat she's tied to, can Homura treat her any differently given Sabrina's resolve to fight this threat and her own acknowledgement that she could be somehow responsible for it? How does Homura treat someone who is clearly determined to fight her own potential liability to Homura (and desperately does not want to be a liability in any way)? And on top of all of that, Sabrina is actually someone who has known everything Homura has done and been through all along, and has not only forgiven her for everything from the start, but expressed her approval and appreciation for it all? Sabrina knows and understands, and always has, and despite knowing (just like she's known all about Madoka, Sayaka, Mami, Kyouko, Oriko, Kirika, and more), Sabrina believes that Madoka would forgive, understand, and appreciate everything Homura has done if she knew.
Sabrina is going around, changing everything, even things she doesn't need to change, and all of this change is scary and unknown to Homura, but she can't deny the distinct possibility that perhaps things are changing for the better. Homura has been learning the entire scenario and its factors loop by loop, trying to refine her strategy as much as possible to maximum efficiency and effectiveness, believing (or hoping) that she'll succeed once she refines it enough--but this loop, Sabrina has thrown that strategy and dynamic off the rails entirely, and everything is so different. So far, there's been no harm in following along just to see if this loop actually succeeds for whatever reason, but now, perhaps there actually is some real risk of permanent harm--either to herself or to the loops as a whole (aren't they one and the same, really?)--and this muddles the one choice (and clearest choice, until now) she's really had to make thus far, this loop.
