Probably the best thing you can do is be there for your daughter when she is ready to accept your assistance. She is legally an adult and has the right to make her own decisions. All you can do is leave the door open to conversation, advice if asked, assistance. Maybe it would be helpful for you to speak with a therapst for suggestions etc. You would probably feel better about the situation.

Hope your daughter gets her life together and gets away from the abusive boyfriend.