she's kinda a terrible person yes. She has a deep assumption that of course she has authority over everyone she sees as below her, and only really cares about collateral damage to people she doesn't know because her girlfriend would be sad.
It's worth noting that Cirucci isn't using Nemo as a morality chain. She's not Urahara; her thought process doesn't go "I don't understand why things are bad, but people I care about tell me it's bad, so I will not do them." She is perfectly capable of compassion, empathy and moral thinking, but is heavily biased towards people she cares about and towards projecting from their point of view.
The whole thing with Nemo being axiomatically opposed to collateral damage has a tendency to obscure the mechanisms of Cirucci's thinking, because it
is a situation in which she thinks "well, I wouldn't necessarily mind, but it'd make Nemo sad, and that's bad," so let's take the example from a different angle.
If we remove Nemo from the picture of the Karakura Sacrifice Scheme, there's still Ichigo. He's someone Cirucci fought with twice, abducted to Hueco Mundo, and whom she finds interesting enough that she talked with him and sparred with him since he's been here. She finds him entertaining and sympathetic, even if she will never stop trash-talking him. He's sort of a very fierce but dim puppy.
If you told her "Aizen is going to murder Ichigo's home town" after these facts having been established and ignoring Nemo as a factor, she'd think that's bad, because that's where Ichigo's friends live. It's not the kind of cold computation Urahara does where it goes "friend would be sad, therefore action should be avoided." She'd legitimately think that it's a terrible thing to do, on an emotional level. Aizen wants to kill people who are cared about by somebody
she (sort of) cares about, her second-order empathetic circle, so to speak. And that's wrong.
But if Aizen sighed and said "fine, then we'll blow up that random midwestern American town instead," she'd nod sagely and be satisfied, because who cares about
these people? She'd still think that's bad, because murdering thousands of people is bad, but you know, fate of the world, omelette, eggs.
Or to take another example, if in a STUNNING UPSET WHAT A TWEEST the next update had Grimmjow appear in front of Cirucci with a Snidely Whiplash moustache painted on his face and gloating that "actually I was working for Aizen all along, sucks to be y'all," she would first be shocked and surprised,
then she would be outraged at this betrayal of her, and
then she would be even more outraged
on Luppi's behalf, and she would likely attempt to avoid killing Grimmjow as much as possible in the inevitable fight that ensues, because he did something terrible to someone she (will never admit she) cares about, and he needs to be alive and conscious when she tosses his smoking body in front of her least-favorite Fraccion and tells him that it's up to him what he wants to see done with his treacherous lover.
I'm drawing in very broad lines here, of course. Cirucci's outlook on these isn't
naive, she is cognizant that this isn't really a coherent ethical system and that it makes her selfish. She just considers herself exposed to such pressures that she can't
afford to get philosophical about it and that she
has to focus on the people she cares about ahead of all, and part of why she loves Nemo is that Nemo manages to be more deontological even under greater pressures than Cirucci's own. She finds that inspiring. A little uncomfortable sometimes - when you deal with someone who is more ethical than you it's hard not to feel like their actions are telling
you that you're a bad person, even when it's not the intent - but she's a mature person who can deal with such feelings without letting them taint her relationship.
Or in other words:
Cirruci's big intermission with Syazel was called "Care Ethics" for a reason.
Care ethics are probably what Cirucci would come up with as a coherent ethical system if she were given time to think without the constant stress of life-or-death stakes surrounding her as a rebel in a dimension-spanning war.
This is all further complicated by her aspirations to nobility. To take an example, Cirucci has very little emotional connection to Ren: he is a set of valuable knowledge packaged in a dull and unpleasing human envelope. She literally pressed him into service against his will, then later told him "you can go now if you want," and when he chose to stay she considered the matter resolved with no real wrong done on her part. She doesn't really care about him as a person. But if someone dropped by the Red Chamber while she is away and murdered Ren to get at her, she wouldn't just be upset that she lost a servant; she would feel like
she has done wrong, that she has failed in her obligations as his mistress. She failed to assess the need for protection one of her servants had, and in doing so caused his death, and that is a terrible moral fault. One in which, in fact, she may be
more culpable than whoever killed Ren, as they just opportunistically seized a chance to hurt her like any enemy would, whereas she actively failed in her duty.
Basically gestalt-ghosts learning humanity after centuries as cannibalistic beasts have confused moral codes. See also: Most Moral Fraccion, Nemo Elcorbuzier, whose entire ethical system is predicated upon having Deadpool-tier regeneration.