Try not to take it personally. Honestly. I know it's easy to say and hard to do but seriously...
This has happened to me countless times...I ask a friend if they want to do something later or the next day or even weeks in advance and they say "Oh yes, that would be fun" or whatever. And then, while to me, that means I have committed myself to that activity, that person, that time...to some people, it doesn't mean anything. Even if they make the plans with me, they still feel it's OK to change their minds, often without notice. I can't stand it but I've learned to live with it. I know EXACTLY which friends to make plans with now and which to assume all plans are "optional" with. I have one friend who just absolutely refuses to make ANY plans at all...If she is around, we hang out. If not, we don't. I have just learned to enjoy the time I do spend with her and not worry about "next time."
I love to do things, be out of the house, be with friends and other people and I CAN'T STAND it when I am looking forward to something and then plans change and I'm stuck home or alone....But I adjust and so will you!!
Now if she is just a jerk, that's a whole different story!! Anyway, we're happy you are here with us tonight!!