C.C.
I'm hoping you have a restraining order against your ex husband.
A 12-yr old is experiencing the first parts of puberty... which is her independence. Messy room, etc. is normal. Although we don't like it, about all we can do is harp, try to bargain and probably just be frustrated in the end.
My experience was with a son who had a messy room... one day I went in and cleaned it and threw something away accidently which totally pissed him off. What I got out of it, after the anger was over, was a perfectly clean room. I also got him a twin sofabed and coffee table... and a table for his TV and it was like a living-room/bedroom. His friends would hang out there.
I wish you the best of luck.