Certainly when she is 18, she may do as she wishes in terms of moving in with your family. In the meantime, if it is safer at your home, she should consider moving in with you - does she really expect that her parents will initiate a court action to make her return to them in a home that is without basic utilities? Is it possible for her and your son to have a talk with her parents in order to reach an agreement? That might be a good approach. Failing that, she should consult an attorney who can review the entire situation with her and give her options, including referrals to local agencies that may provide help and shelter to mothers who are minors.