My friend is in an abusive relationship and I don't know how to help her?

Wow. I think you should talk to her again. And tell her parents for sure. Also, try to get evidence of him doing it and turn it into the police. He needs to go to jail. That is soooo ridiculous! Nobody should have to go through that! You need to do something about because it don't seem like anybody else is! Even if she hates you for it, one day she will thank you and y'all will be closer than ever!