Quoting Jude the Super Kinkster:" Legally she has to give you 30.days notice."
Actually no she doesn't. Unless she was renting an apartment or house or room and signed a contract and pays rent.
OP: Best bet is to just move out if you can afford it. If not find something to do and be out of the house when your MIL is home. DH and I were living with his parents when our first was born and they kicked us out cuz they wanted to replace the carpet>_< So we had to live with my parents because where we were waiting on our apartment application, they didn't have an apartment ready when we had to leave his parents.