Fortunately I have not been in your situation, but my BFF was a couple years ago. We had this friend that I was no longer close to and would only see maybe once or twice a year, but she would always call my BFF and talk about how bad her life was and cry to her about how she slept with some random guy from the bar and he never called her afterwards...yada yada yada! Anyways, there is a big party weekend in our little small town Aug long every year that causes the towns population to more than double, and my BFF decided that was going to be the end of the friendship. It was sort of like a goodbye although the other girl was not totally aware of it. It actually worked well, as the other girl only tried to call my BFF twice I think, and that was it and it has been over 2 years since then. Of course you have something else that you would like to do, so I don't really know what to tell you. I think that this "friend" is to draining on you to keep around, but it is just a matter of when you cut her lose. Is the ticket paid for? Did she pay for it? Is there anyone else that could go in your place?