When I was 16 I dated a girl who had been sexually assaulted by her mentally disabled twin brother multiple times. After some time she got admitted to a mental hospital. As far as I knew it was because of clinical depression. We called every evening and I visited her a few times. After she got out, she told me she suffered from PTSD, but insisted to not let it get in the way of anything. But the more serious things got, the less she wanted to do something together. Apparently having a relationship increased the intensity of her flashbacks. I eventually broke up with her because she strait out refused to do anything with me for over a month.