You, literally, cannot imagine.
Her "issues" had "issues".
Full disclosure: That said, my middle sister has made great progress since I rescued her from her psychological black hole. She is very smart, but had simply shut down her brain, due to oppressive spouses and prolonged systematic abuse. One physically beat her, the other emotionally beat her. (And that's not even considering her first 2 husbands!)
In conjunction with her doctor(s) I helped her out of her shell. I do have to give her credit for trusting me and allowing me to help her. Learned behavior is an enormous thing to overcome. I will admit, I too made mistakes along the way, but that was largely because I didn't understand what I was dealing with. Over the course of two years, I became acquainted with her irrational fears/phobias etc... and her veritable litany of illnesses. Plus she is a veteran drug abuser and is it really any wonder? Finding out a year in that she also suffers from substantial hearing loss explained MUCH, but if you don't know someone is half deaf you assume to they either nuts, stupid or whatever.
Before she left I told her that I was her eternal well-wisher and that I sincerely wished that she continued to learn new things. (I'd introduced her to Intersectionality, Gender Studies and 3rd Wave feminism to stimulate her dormant brain centres. It IS working, but again, it is a slow process. I implored my eldest sister, who is taking her in, to continue to help her learn new things to continue the "therapy" as it IS showing results.
It's been a very long two years.... (sorry to dump, but I need it.)