I have a 13YO sister who is giving my mum hell at the moment and a mother of one of her friends does the same... i find it incredibly frustrating and totally think she is over stepping boundaries.

Not sure about the sharing a room thing, i have NO experience but i think if you say no and she does it anyway there will be resentment yet if you say yes and give it a month im sure she will get sick of sharing a room...i dunno, just thinking out loud. As long as she knows she is welcome back anytime i think that the stress of yr 12 plus sharing a room, she would probably come home on her own? Or maybe would she be too proud to come home? Oh i dunno.

Big hugs to you tho!! I hope it all works out for you guys! xo