Been there Hanginginthere!
Boy have I, had a best friend growing up who became much of the same. It got worse over time & became a very one-sided friendship. We'd make plans for lunch or something & when we were seated she'd say she didn't really have any money or "couldn't" cash her check for some weird reason.
At first I'd be nice and loan her the money, if it was a small amount I'd never see it again! As we've gotten older, she's moved back home several times since she squanders her $ but works full time making almost what I do-so I decided it was rediculous to give her money, even though its nice to "treat" sometimes, because I have my own household to support, and I just don't live irresponsibly off others!
Definately talk to you friend about what is bothering you-otherwise it will keep on happening and make you bitter towards your friend, with mine I was, she just didn't realize that she treated me & others that way, not only with $ matters.
Since it didn't seem to bother her that it bothered me when I talked to her, we don't really see each other anymore-I want to stay focused on the important things in my own life and not here about her latest money crisis <as she tells me about the new jeans she bought-ahhhh> I do miss her, but not the babysitting! Enough of my ranting....good luck with this, I know its a hard subject.