I really like the flipped mindset in this story, getting to understand the collaborator's side, and the clear illustration of how privilege and the lack of it affect the characters' perspectives.
I don't understand why the protagonist was mad that Leonardo "ditched" her when she had made it clear to him multiple times that she wasn't interested in his revolt. Really, he would have been foolish to give her any details of their escape plot.
However, I doubt the aliens will just kill him -- why drag him back in chains if so? Just to test her? Certainly sinister, but I'd bank on "re-education" (torture/breaking) for him instead.
I think it's right that we never find out the aliens' true motivation -- making earthlings into good slaves, or genuine uplift for us, from their patronizing point of view? But the protagonist has no way to know, so neither do we.
I don't think of her as a sociopath for not caring about her parents' fate, since we don't know how the parents treated her. She does feel a little regret and concern for her sisters, but not enough to do anything about it; I would certainly try to find my relatives, but I haven't been beaten down by life the way she has.
I think she's deluding herself about the music, though; she says it completes her, but it seems she's using it as an opiate or distraction from reality instead.
I didn't really notice the swearing, so either it worked seamlessly with the character or I'm dead to all proper feeling (I work in a newsroom, so the latter is at least as likely). I think maybe the fact that it's audio also lets it slide by easier for me than if I read it, because I'm used to ignoring it in movies, etc.