I feel like a bad parent.....

My daughter is extremely abusive in her relationship. Everyone sees it. She is verbally and physically abusive. She's always had anger issues and was in therapy for them, but as soon as she turned 18 she refused to do therapy. She's put her hands onbme a few times. I've told her time and time again she can't treat her boyfriend that way. That she needs to stop putting her hands on him. To stop putting him down. She called me a couple nights ago because she was arrested for a domestic dispute and she hit him in the face with a hot pot she was cooking with. Her dad is trying to get the money to bail her out. Her boyfriend came over and seeing what my daughter did to his face killed me and made me feel so guilty. He said he wanted to talk to me and started crying saying he doesn't know how to make her happy and he feels useless. I asked if he wanted me to be honest and he said yes. I told him it's not him, it's her. And he needs to leave her. She might not change and he doesn't deserve this. I explained that I know her better than anybody and he needs to leave her. Now I feel terrible for saying this about my daughter. Am I a horrible mother?