Thank you for stopping by the Disney with such a great question, Jennifer! We are honored to be a part of your family vacation by guiding you around!
I have a picky eater at home myself, so I know what you're talking about! While some
dining locations will allow you to bring in some food products for your little one (they will not be able to heat or reheat for you though), some other places will not. The best way around this is to ask upon your arrival at the Walt Disney World Resort. You can stop by your hotel lobby and ask Concierge to get in touch with the specific dining location to clarify this.
If you have a special request for your little girl, the chefs will work with you to try and meet her needs. You may send them an email at Special.Diets@DisneyWorld.com to ask whether they would be able to modify a food product to meet her needs.
Jennifer, I hope these thoughts are helpful and I wish you and your family a wonderful Disney vacation!
Have a magical day!
~Desiree