Hi Emily!
Just being in Walt Disney World will make that day even more special than usual!
Make sure you stop by Guest Relations and ask for a special "Happy Birthday" button for your daughter to wear on her special day. You'll be amazed how many Cast Members will notice and wish her a wonderful day! And, you never know...some extra special Pixie Dust could get sprinkled her way, too!
How does she feel about Pirates, instead of Princesses?
The Pirates League is great for girls, too! It actual offers an "Empress" Pirate package, as well as a "Mermaid" package!
Disney's Family Magic Tour is described as a "two hour interactive quest" to save the Magic Kingdom from a Disney Villain! This is something the entire family can do together!
There is also a wonderful Character Dining Experience at the Crystal Palace with Winnie the Pooh and Friends! Call ahead for Advanced Dining Reservations.
One more thing to check out:
Customize Your Celebration with one or more of the wonderful ideas on this webpage - a special cake can be ordered ahead, create a special t-shirt, or order special gifts!
I hope these ideas get you started, and that your daughter has an extra magical birthday!