FW - you poor thing. The whole thing has been sorta like black mail hasnt it. "I didnt get my way with you, so i'm going to go live with my irresponsible mother" Whats wrong with the world today when kids can do that!
I really feel for you. We had a sorta similar situation with my cousin. My parents took her in as she was kicked out of her foster home, and when she didnt get things her own way, and had to hand over the drugs etc, decided that was no fun, so moved back home with her mum, so she could have all the drugs and boys she wanted. (her mum is prost BTW)
As for being 13 - call me an old fashioned farm girl - but, it never would of occured to me at 13 to be that interested in boys that it would be a concern to my parents. But, that was my upbringing and life style as well - home schooled in remote area, then shipped off to all girls catholic boarding school.
I hate to think how young my kids are going to start being 'interested' in the opposite sex - 10years old and pashing and getting stiffies! OMG - they should be still playing with power rangers and tonka trucks! ....... I am in for such a shock i think!