Mother in law

How long would you say is too long for your parent(s) or your SO’s parent(s) to visit your home? My SO’s mom was only supposed to stay with us for 2 weeks but 2 weeks turned into 1 month and when I brought up when she was leaving my fiancé told me she wanted to stay 3-4 more months. He made this agreement with her and told her yes without talking to me first and now I want her to leave he has an attitude. I don’t even allow my own mom to stay this long and I was never okay with his being here this long. I’m at a point where I want my space back and I feel like she’s trying to take over my home.