I'm sure she must be really disappointed. We spent our holiday in April going round all the shops to find my daughters dress for her prom (ok the school called it a summer ball but the girls have decided otherwise), and I know how disappointed she would be to miss it. She really felt like one of the locals as it was April and they were all looking for their dresses for May.

I dont think your daughter would feel right at Arabian nights to be honest, knowing how self conscious they are at that age.

As someone suggested there might be somewhere in Disney.

You could try a search on google under formal dinners or something like that (course it means all the family will have to dress up as well. If not why not arrange a special meal or nightclub trip in the UK with her friends (if they are all dressed up - if shes anything like my daughter, she wont mind if they arent dressed the same as everyone else).