CW: sexual assault, mental health is important, please prioritize that over reading this.

My life partner and I had been living together for 4 year in an open relationship. We had been romantically separated for 1 of those years but still flirting/kissing/having sex with each other in our shared home. A girl (26) that I had known for 15 years needed a place to stay, as she was being financially abused by her former boyfriend. I offered to let her stay rent free at our house to try to save up money to move out by the new year. She was sleeping in my bed until her old one could be retrieved from her ex. The girl and I had been sexually entangled when we were in high school, but this was obviously a living situation where it was inappropriate for things like that to happen with her.

I knew she had a problem with drinking. She used to have a problem with drugs, and I was trying to prevent her from being in a situation where she was likely to relapse. Despite one of the house rules being keeping her drinking in check, she repeatedly came home drunk from work and continued to drink. It got to the point where she got into bed after I had fallen asleep one night when we had been drinking together and grabbed my crotch while she was sleeping, refusing to wake up to talk about it and pretending like nothing had happened afterwards. So... I pretended like nothing had happened too. For a while. Took up sleeping on the couch near my partner's room just to feel safer about the situation. I let her have my bed. I was fine with that as long as I was away from her.

But then she decided to start sleeping in my partner's bed. I had a full on fucking breakdown. It had been about a month since the events happened and my partner didn't believe me when I said I didn't feel comfortable with this girl sleeping in her bed because my partner has past sexual trauma like I do. I tried to handle it for while through the holidays as they continued to sleep together in our shared home, but finally I couldn't do it and told the girl she had to leave. My partner chose to go with her to find her a place to stay, so now they're staying at my partner's mom's house together. I feel like conflicting sides are telling me different things. Everyone from my partner's side is acting like I am tearing her life apart willingly when she is the one choosing to leave me and side with the person who assaulted me. I'm trying to move on from this, but I'd be curious to know Reddit's opinion.

Tl;Dr My best friend assaulted me and my partner left with her when I kicked her out. Am I in the wrong?