Agree with all of the above. Your well within reason to be damn pissed. She is definately taking advantage of your generosity. If I were you I'd look for a replacement room mate. She probobly is a friend, but any true friend wouldn't be fucking you like this. 1100 is a big loss, but it might be worthwhile to just forget about it and get her out of the house to prevent further issues. It sounds like she will just continue to run up a big tab with you that she can't pay off.