At 18 years old, she's just learning how to set boundaries in relationships. You don't really have the power to break them up, and trying to do that will not only be ineffective, it will also cheat her out of the lesson she is learning -- how to set and maintain appropriate, healthy boundaries in relationship. It's not your job to determine the course of your adult daughter's relationships, but you can help her figure out how to take a stand for her boundaries.
For instance, if she tells him that she won't be in a relationship with a man who doesn't respect her physical boundaries, and she remains in the relationship, telling herself that he stopped doing it so much, the only things she's teaching him is that it's okay not to respect her physical boundaries, and that she doesn't keep her word.
To set and maintain a boundary that means anything, she must keep her word when she tells him what the consequences are of not respecting them. You could help her to set a boundary she can live with, whether it's an all-or-nothing boundary or a three-strikes-you're-out boundary or whatever. She'll probably need your help in being strong about bearing the consequences herself, because it can be hard to bear saying goodbye -- but she's not doing herself or him any favors by saying one thing and doing another -- she's just effectively signing an unwritten contract
that it's okay not to respect her.