What an uncomfortable problem, on all sides. I find myself wondering whether you've tried to talk to your daughter about this to get her take on the whole business. She might have some information that would help you all make more sense of it.
There's a fantastic book that helps parents (and kids!) work through all sorts of struggles. Check out the book Faber and Mazlish, How to Talk So Kids Will Listen, and Listen So Kids Will Talk. The authors have years of experience teaching parents how to help their children identify and communicate their feelings and needs, and participate in finding their own workable solutions.
They also teach parents how to communicate their own needs and concerns in a clear, understandable, and respectful way.