My mother-in-law keeps asking for money? What do we do?

I'm a newlywed. My mother-in-law keeps asking us for money. While we can spare it, it's preventing us from getting out of our student loan debt. If we don't help her out, she might expect to live with us (she has mentioned that before) and I don't think I could bare it. I don't mean to sound selfish, but I'm a newlywed and I'm very clean while she is very messy, etc. etc. My husband gave up a masters program to help her out financially. I know she is capable of getting a job. She just chooses not to. My husband is worried that she'll end up on the street but I feel like her situation is her choice. What do I say to my husband and how do I handle this?