Did my husband try to sleep with his step sister or is she lying???

*Long post*

Forgive me for the long post but I’m torn. I would appreciate a second thought since this is something I can’t talk about with just anyone. So.. 7 years ago before I knew my husband his step sister gave him head. They were drunk whatever. Recently my husband was at his brothers party late and they were all drinking and I felt weird cause she was there so I made a joke saying don’t fuck your step sister.l cause they were playing beer pong in the garage alone. He got mad cause I threw out dumb past stuff. Few days later at his brothers wedding we were all drinking and his sister seemed off. Didn’t think much of it until she offered to buy me a drink and she got in an argument with someone else and her step mother came in very mad. So his sister was upset and wanted me to go in the bathroom with her, my husband says that’s bad new and laughed it off. She was venting to me and the person I am I had her back. She proceeded to tel me that my husband grabbed her ass during beer pong and when they sat in the car together he tried to make moves and refused to leave her car when she said to, and that this has been on his mind since graduation. Telling me that I deserve better. Shook end up by this I stayed calm and thanked her for telling me. Came back out and my husband was in his way to the ER cause he punched the wall and broke his hand and thought I was going to leave him cause of these BS rumors going around. He was talking to his mom about it cause his sister told his mother the same thing. My husband was upset that I believed her cause she has a bad track record of lying and getting emotional when drunk. She accused her dad of molesting her and got her uncle in jail for saying he did also and a few others. Her uncle was found not guilty and claimed that it was false. Her entire family believes she is lying cause she does this thing. My husband said that night when they were talking she was crying and upset about her relationship and a ton of different things. He told her I knew about what happened at graduation and she was upset cause she has never told anyone, especially her husband. So my husband is pleading for me to believe him, and is being so nice about how he will become a better man for me because of some previous minor issues we talked about also. So here’s my thoughts... my husband isn’t a very sexual type. He has never been. That’s fine. Whatever... anyways it is a little hard for me to believe this cause that’s not how he is. But he also wasn’t texting me at those times that night. But swears on our sons live that he didn’t do that. But he’s also flirty when drinking. Not flirty but friendly. This I already knew. So my theory is that when I told my husband not to fuck his step sister.. I was told by his brother that this pissed him off and he came in shouting that I said this. I wonder if this pissed his sister off cause it was personal info and she’s mad at us for being verbal about what happened at their graduation night. So in theory she wanted revenge and tried to hurt our relationship cause maybe We hurt her. And thought we might screw up her relationship so she’s playing victim. She seemed SO damn convincing though. But idk what to think.