I've had a similar, albeit less contentious, situation occur with my in laws helping us move. When we first made our move from Iowa to Illinois they helped us, and I was grateful for it. But when it comes time to decide where stuff goes and the mother in law tries to tell us how to decorate, that's when I get a little annoyed. At one point she tried to tell us where the tv should go, and I calmly say "You won't have to deal with the glare from the window, I will." I figure it's a clear enough signal, but I said it kind of jokingly. Next she's trying to tell me where to hang pictures and stuff on the walls and I about lose it. Just before I start saying something about how "this is my apartment and I'll decorate it however I ******* please" the father in law steps in and says "leave the kids alone, this isn't your apartment." I don't think I've ever been more grateful in my life. I think he read my face and saw that I was about to blow up and stepped in and took care of it. I owed him a beer for that at least that night.