Whatever she wears will be fine. The princesses are super sweet here -- we met Ariel in June at dinner and were thrilled! Have a great trip!
No need to dress up. We went in August and only a few girls were dressed up.
Glad we didn't though because it rained incredibly hard right before we got in, and there is no dry place to stand while you wait.
We had an amazing time no matter.
I found Akershus to be the best meal. The food was good, and the princesses were amazing.
Enjoy