I believe in being honest! Just say "It wouldn't fit with our life style. But I can help you find an apartment". Why do we feel we must comply with weird requests to avoid hurting feelings, etc. Think of your own life first. That doesn't mean be selfish, but that is a huge thing to ask someone! If she has the nerve to ask, then you'll probably never get her out, you'll find reasons to leave your own home, and it's just not worth it!