Oh hell Maura!!!! She's in California, right? I'm going out there on June 6 - give me her address because I am totally going to go and kick her ass into next year.
I'm sorry, but what a f***ing c**t! I mean seriously... who does shit like that?!?!? Except for immature, selfish, nasty, bitchy people that we don't want in our lives anyway!
I hate to say it, but it's time to stop trying. You know that I, of all people, wouldn't say that unless there was absolutely and utterly no other choice. But it sounds like she's been poisoned by your mother or something.
So, vent, rant and rage, and then forget it and move on. Because she's simply not worth the frustration. Hopefully someday she'll come around and figure out that she's violated the trust of someone who is wonderful and generous, but she's not going to realize that until you're not there for her.
You paid for her dress, didn't you? I'd demand that she reimburse you - even if she doesn't, making the demand will make you feel better.
Big hugs my dear!!! You know if I didn't have other plans, I'd be there to step in!