Family members as roommate's????

Okay my fiance and I have been together going on 3 years and his mom and I get along somewhat okay. She has lived in 4 or maybe even 5 different places in this time period and can not even get utilities in her own name. And now she wants to know if she can move in with us "just until I can get on my feet", granted rather that she is currently living with her husbands sister and boyfriend. Am I wrong for not wanting to let her come stay? I mean she has had plenty of time to get on her feet while living with them and to have moved that many times already I honestly feel like she's just looking for a free ride as long as she can get it. Am I a bad fiance for feeling this way? Sorry so long just had to vent.