Hi Stephanie!
I'm so excited that your daughter will be able to have the most amazing experience at Disney's Bibbidi Bobbidi Boutique! The Fairy Godmothers will transform her into the most beautiful princess, and having listened to the magical pixie dust ceremony, I can tell you now, you will be wanting some pixie dust your self.
The morning of her BBB experience, you have a plethora of options! You can take her to enjoy a morning at Magic Kingdom, surrounded by Cinderella Castle and the fantastic attractions in Fantasyland.
You may want to do a late breakfast at Cinderella's Royal Table, or perhaps Akershus Royal Banquet Hall. Being able to dine with the princesses is such a cool experience, that it will definitely lend to the magic of the day.
Or, perhaps an afternoon tea is in order. I'd recommend
My Disney Girl's Perfectly Princess Tea Party. Taking place at the Garden View Tea Room, at Disney's Grand Floridian Resort and Spa, is geared towards princesses and princes, aged 3-11 and they are entertained with stories and a visit from Princess Aurora. All guests are served a prix fixe lunch and "tea" (juice). Younger guests are encouraged to dress as their favorite Princess, and if you have purchased her gown ahead of time, this could be a great segway for her magical transformation!
Hope this helps you plan your magical vacation!