I hate my mother in law!!!

My mother in law is the WORST! She is a drug addict and has been for 20 years. I do not like her in our home or around our daughter because she is so unstable. She's cussed me out in our home, admitted to being high around our kid, talks bad about me to my fiance, stolen from us...

Well my fiance let her come do laundry at our house which I was against, but it's his mom so whatever. Well, she stole an entire basket of my clothes!! This is not the first time she has stolen my clothes, but I was not expecting that while we were home with her. I'm so pissed. My fiance says I'm just confused and trying to pick a fight with his mom and she denies it. This bitch just wont stop! She's a psycho.

Should I forbid her from coming over? Our house is in my fiance's name, so can I even do that?