hello, I know that this is hard for both you and your BF. I have one suggestion, call the Boys Town National hotline. 1-800-448-3000. They are a great resource and they may know of a resource close to where you live that can intercede between father and daughter. It also sounds like she is grieving the fact that mom is not at home.
She may be 17, but that does not mean that she could not use some counseling