You have a fantastic opportunity here - this should be a growing opportunity all parties. Make rules as a guide for her and explain it is not just like a family situation but an adult job situation where you lose your job if you break company rules. She's not moving into a dorm or a sorority house where she can just go nuts - she has to look at it like "this is my chance to reach my potential" and if she follows through will end up with a great life ahead. Her parents seem to have a limited view of the world and you can help the child "make it". Her parents may also find you as a great "next step" for all thier kids - so put up a boundary and say "one only" if you feel like offering this opportunity to the one child. Otherwise, be prepared for the whole crew to come through your boarding house :-)