At Princess Fantasy Fair, you are not guaranteed to see any specific princesses, we asked several times which princesses were in there, and the CM said "all of them" take turns. So the princesses that are there when you get in line may be different when you reach the front of the line.
We had eaten at Ariels the day before and had seen Cinderella, Belle, Snow White, Sleeping Beauty, and Ariel. We ate at Goofy's kitchen that day and had seen Jasmine there. The only princesses we wanted to see were Pocahontas, and Mulan, and the CM would not tell us if we were going to see one of them at PFF. So there was a good chance we would stand in line for an hour and not see either of them. So we left, I hope you have better luck.