Mmmm ... I don't think you should have SIL over to stay. She and H are taking advantage, IMHO.
Boundaries sistah, boundaries. Just say, "sorry, no can do. Got other plans."
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim