At this point there is very little you can do. If she refuses treatment then you cannot have her committed without her permission, unless she is declared legally incompetent and you are made responsible for her. You can report it to the police, who may or may not investigate since you have very little information to provide them with. Even if you knew the man's name and address, they may not investigate since she is consenting.

There is literally nothing you can do that will guarantee that it will stop.