Been there, done that. I have lived with MIL and FIL a couple times (we just moved out of there recently after living there for a year) It was hard because she was a total slop and I'm not. But we made it work out, she had her side of the sink, I had mine. So if her side filled up with dishes that's her business because I would always do mine. We each paid our own share of the bills and bought/cooked our own meals.
I would have to tell her when to do chores though, we had an understanding that the bathroom and upper floor was my job to keep clean and the kitchen (besided any messes I made) and living room was her job. She would literally go weeks without cleaning and I would have to get on her about it, one of the biggest reasons we moved is that I couldn't take it anymore.
I spent a lot of time in my bedroom which had a TV and computer in it, so I didn't really have to see her that often. I think we get along better living apart.
Unassisted birthing, atheist, poly, bi WOHM to 4 wonderful, smart homeschooling kids Wes (17) Seth (10) Pandora Moonlilly (6) and Nevermore Stargazer (3) Married to awesome SAH DH.