Oh my! What a complicated situation.....I'm so sorry you have been forced into this mess!!! First off, I totally agree with Sadface. While this girl is in your home she has to live by certain rules!! YOUR rules!! Your BF needs to sit her down and set some very clear boundaries.
More to the point though, this girl is not your responsibility! I don't think it's right that your BF is scared to "upset" his family at YOUR expense. He needs to put YOU first (((((((((anjelmarie)))))))))))

I really hope you can work through this with your BF and that he starts getting his priorities straight