>>713861180 (OP)>complete psycho while her "brother" is still alive>lives with him half naked>talks about how she was going to kill himMy headcanon is that he used his tech-skills to put some kind of behavioral chip into her, like a hacked Doll chip or something, and was keeping her as a freaky sex slave. I wouldn't bet on the others knowing about it, but I also wouldn't bet on them asking too many questions at the time.
At any rate, she has her immediate freakout when he dies, but then right after she started to mellow out. By the end of the series she seems to be as chromed up as peak David, and has been a balanced, functional cyber psycho for longer than he's been chromed up, period.