Was I Wrong?

Heres a little info first, my best friend is 22 her man is 29. Neither have a job, he mooches off his mom, she just recently moved back so she's looking for a job. He Haas made no effort to look for a job. Sometimes they come and stay t my house with me. He's kind of psycho. He cut her name into his leg, threatened to kill her if she left him. They're always breaking up and making up. Its infuriating. Especially since it happens at my house. Anyways on to my story.

My best friend and her boyfriend got in a fight. He hurt her feelings and they started arguing. He took her car keys and hid them. When I went to find them like she told me to, he told me I could go f..k myself. Well she heard it and went ballistic. (This is all happening at my house) well things got bad after that and I watched him grab her head and slam it into the door. She fell down and cried so hard. 20 minutes later they were fine again. Well the next day she couldn't remember what happened, or how she got the cut on her head, so he lied to her and told her she fell. She told me what happened and I told her he lied to her and she didn't fall, he slammed her head into the door. She was like well we're back together. I told her I couldn't support her and him being back together if he put his hands on her again. I told her I wouldn't stick around to see it. That she could still have me as her friend but don't expect me to wanna be around him. She was hurt. Was I wrong?