Yeah, that sucks, and pretty rude of her. Trick I learned is that if a girl mugs you off without a very valid and genuine reason (as yours obviously did), then remove her from your phone and from Facebook and move on.
There is zero point keeping them on your phone or checking their activity on Facebook as it just makes you more annoyed and you end up feeling worse. Usually when they see you removed them they will display faux-outrage and message you asking whats up, or making silly excuses, or trying to get a response (her pride is dented that you dared to choose to remove her, guys usually don't do that to her), but unless you are in love with that girl then just ignore and leave your precious dignity intact.
In summary: ALWAYS listen to the little voice inside your head. If you are doing something that doesn't feel right, or she is doing something that makes you feel crap, then it's simply not worth it. Never go crawling back or re-add her because you just give her license to do it all over again, which she almost inevitably will. Just keep in mind: if she gave a **** about you then she would not behave like that. End of.
I now do my best to follow that ethos religiously, and it works.