Thanks for all the advice. We spent all day Sunday shopping for a Costume. We went to Target and they had some, but were too small (they didn't have different sizes, only 3+). We tried Toys R Us and they didn't have any except Barbie, we then went to Party City and they had some pink and gold wings and a skirt and wand set, so she decided to be a pink/gold TinkerBell instead of Belle and I was only out $20 which also included a plastic hook for my son to be Hook. We have a pink leotard and ballet shoes and tights. It's actually better since she looks AWFUL in yellow. I will be sure to bring a change of clothes for her on the day she wears the costume.
Now the problem is not letting her wear it until we leave. She did try it on once to make sure it fit and that she liked it.