Most 3 year olds are just fascinated by princesses, so I would do the BBB (bippidi boppidi beautique). If possible, go to Cinderella's Royal Table or Norway's Askerhaus. But even things like playgrounds, such as the one in Dumbo, or Innoventions at Epcot, will keep her fascinated. My son loved the Piggy Bank activity in Innoventions at Epcot. It's above their head what they are really doing, but they love carrying the pig from station to station.
There is so much to see and do, I doubt you'll have any trouble finding things to do to keep your daughter interested in all there is to do!