Future mother-in-law wants to go house hunting with us. My folks aren't going, why should she?

My fiance and I are looking at possible houses on Thursday. His mother heard about it and wants to go. I don't get it. She won't be living with us and the decision is solely mine and FH's. We are both adults, have good judgement and his best friend is a realtor, so we are not likely to get a lemon. I don't want FMIL sticking her nose in and making unwanted comments and suggestions. My parents aren't going because they trust us and don't want to control us. How do I get the woman to back off and get a life?