H...it sounds like a miserable experience with your MIL staying with you especially as you are going through this. I hated it when my MIL came to town, she always came for a week and was worthless the entire time she was there. Slept all day and stayed up all night renting pay per view movies on my dime. I think I would spending a lot of time by myself On a serious note be confident and don't make them feel like you are a guest in your home. F that.
I like the Fonz analogy...be cool, nothing bothers H because he is confident and the man!