Can you splurge on Cinderella's Royal Table for one of the meals? That's about as special as it gets, what with being right inside the castle and all! If not, who are her favorite characters? Pick a character meal that features her favorites (we love breakfasts for our character meals, but you have your choice of all three meals, so pick whatever suits your family best). Then, think about which park she'll want to spend her special day in, and line up your other choices based on location. From our family's experience, having to run hither and yon just to make a full day's schedule of ADRs is not fun, but having choices lined up that are convenient to where we plan to be makes it all a blast.
You really cannot go wrong -- birthdays at WDW are special no matter what you do!