Need advice- mom visiting!

My family is all out of town. My mom wasn't sure she'd be able to afford to come visit, so we hadn't really planned anything. Today she called and said she found some inexpensive plane tickets and was wanting to come visit. My mom does not have a lot of money, and so I asked where she was planning to stay and she said with me! I live in a 3 bedroom town home with my husband and soon our baby, but my younger brother also lives with us in the basement bedroom. The only place for my mom to stay is the couch, which she said she is ok with. My mom can be very difficult and sensitive. She gets her feelings hurt really easily. She really stresses me out when I'm around her. She's also a smoker and smokes a lot, which I really don't want around my baby and my home. In general, I don't like being around a lot of people, especially in my home. I am pretty particular with how I like things and also like my space. I really don't want anyone staying with us, not even just my mom. I feel very unsure how to handle this situation. If I say she can't stay with us, she will definitely be personally offended, no matter how I phrase it or explain it. She will feel like I don't like her. And if she can't stay with us, I know she can't afford a hotel or anything, so she probably wouldn't be able to come at all to see my first baby. My husband has family here and they live nearby and may be an option for a place for her to stay, but again, she may be offended or not have transportation to come visit during the day. I really don't know what to do. I'm due in 2 weeks, and wasn't expecting any one to come visit and now I have to figure out how to make this work. Any one have to deal with this already or have thoughts?