Hey Melissa
Dont take it personally, maybe she just feels weird comming. Does she know other people that are there? Maybe she would feel left out or something? Thats is really rude though and I would be kind of pissed. If she has not intentions on comming she should have just been honest in the first place. I probably would not say anything, especially if shes not that close of a friend, it just may make things awkward. I would just not invite her to anything else in the future. Her loss I am sure she is missing out on a great time!
Hope this helps!
Sarah