What should I do?

Y'all, I have a friend that I'm really close to. Her boyfriend is my Friend since my childhood days and she is just a friend I met in college. So here's the thing, I'm really close with her comparing to her boyfriend and her boyfriend hasn't been treating her right and I can see it myself. Her boyfriend cheats and lies, played her behind her back and when he gets caught and he comes back to her, she always forgave him. Even when she caught him having an affair with another girl and even has a child with her, she still stayed. She told me she is convinced that it is love and starts saying it's a sign and all those things but some days I know she's not fine. She'll always starts crying and she'll feel hurt but knowing the fact that they dated for 5 years, she is not willing to let go. I've heard her say things like, he almost hit her and there was once they kinda broke up and she went out with another guy, he went to look for him and it ended up in a fight. I'm really scared for her. Last week I had an argument with her, I was telling her that a guy was asking my classmate to ask me for a one night stand. And a few days later I told her my ex boyfriend texted me. I also told her that I told the guy I'm recently contacting. Firstly, lemme get this straight. I thought it would be funny to irritate the guy I'm currently contacting by telling him about the one night stand cos I wanted to know if he genuinely like me(turns out he did and still does) and I am not the kind of person that would do one night stand and especially when I know I'm talking to someone right now. Also I didn't expect my ex to text me 2 days later. I felt it is only right if I told the guy I'm currently contacting because I felt he has the rights to know rather than him finding out himself. So yeah I told my friend what happened and all that and she started shooting me with unnecessary remarks. Then I started shooting her back, "at least I know when to back off. Do you? He cheated on you so many times and played you behind your back and you still forgave him. He even has a daughter with that girl and you're still here?". I kinda feel bad after that but I don't cos right after the conversation, she went to twitter to b*tch about me.