My best friend is getting abused and I don’t know how to end it!!

I’ve been best friends with this girl for 4 years, and we’ve gotten so close to the point where people would ask if we were related because we were always together! We were literally together every single day. I even moved upstairs from her with my mother! But recently she started dating this guy, and at first everything was fine. I was happy for her, and i thought he seemed like a nice guy. But then i met him in person. The first time I met him, he didn’t even say hi to me. I just felt like a bad vibe from him and it didn’t feel right being around him. About 2 months into the relationship, she began sleeping over his house. One day went by, then a week went by, then a month, and now it’s been 4 months that she hasn’t been home. She distanced herself so much from me too. Like is she even my best friend anymore? She acts like a completely different person. She says i’m still her bestfriend but my other friends tell her “ you haven’t seen her, you’re never home” and she lowkey gets mad at them. She stays at her boyfriends house, and her mother picks her up every morning to go to school, but this morning she was mad because she had to order a lyft to school. Her mother works late at night and she still tries her best and goes out of her way to make sure her daughter gets to school. But i think that she loves when he gets mad. I feel like she does it on purpose because she gets attention from him when he’s mad. & she does it knowing he has anger issues. Like BAD ANGER ISSUES. He gets mad at her when she’s with her friends, and when she’s not at her house or with him. She doesn’t let her drink alcohol anymore, or smoke hookah with us even if it’s just for fun. She says that he’s the only person she has because “she can’t depend on her family.” But she distanced herself away from all of us already. Her mom works at night now. So she gets up early to take the girls to school and makes it out of her way to pick my best friend up at her boyfriends house. She spends a lot of money on him too. Her dad gave her 40 bucks and she spent it on 4 or 6 bagels. She bought half for him but she only ate 1 and he ate the rest. She doesn’t let her eat, she doesn’t let her do anything. HE DOSNT LET HER GO TO THE BATHROOM ALONE OR SHOWER ALONE EITHER! She can’t even shave her legs in peace, he does it for her. & she has no money 🙁 she’s basically living off of junk food because he doesn’t let her go to the kitchen. He doesn’t let her talk to his mom or his grandmother either. One time she broke up with him to scare him because he did something and then he said he was sorry and he cursed her out and then she said I love you and took him back! After he cursed her out and insulted all of her friends and family calling them all of these mean names, and he yelled at her, and he yells at his mom, and he has anger issues and more bad shit things in his head, she’s still with him! And I don’t know how to help her. All she says was “no he never touched me, he just has anger issues. He’s misunderstood” OR LAUGHS & it’s wrong. She’s had a “urinal infection” FOR A MONTH and she still hasn’t gotten checked out for it either! & I don’t even think it’s a UTI anymore. She’s having sex with him without condoms like that too. He’s so manipulative, and I’m pretty sure he’s abusive, and my best friend doesn’t deserve to be treated like that! Every time I try to give her advice she gets mad and doesn’t listen. It’s like she’s oblivious to everything that happens, and she justifies all of his actions.