I don't know if I should be friends with this person anymore?

So I've been friends with this girl since my Sophomore year of high school. We're 21 now and I'd say we are good friends. There has always been this guy that she dates on and off for as long as I've known her. She always talks about what a douche he is and blah blah blah and that she will never go back to him. Well, there's more to this story. This guy is a major creep. He once tried to get me to sleep with him while he was dating her... I said hell no of course. He has pressured my best friend into letting him finger her and he's been arrested for sexual assault before (I'm not sure if he was convicted). She has also told us that he has forced her to have sex with him multiple times. And he is known to cheat often in a relationship. Me and my best friend have made it clear we want nothing to do with him and have told her that we will never support her getting back together with him. My best friend was so mad she flat out removed her on Facebook... And honestly I don't know if I should even be her friend. She knows about all the crap he does and she still repeatedly goes back to him. She won't listen to reason and I'm so livid right now. I know it's petty but we dislike this guy that much. I don't know what I should do any advice? And let me make this clear I love her, she's great but I don't know if I can watch her burn herself. Ya know?