Hi Sasha!
Each park has Character Meet-n-Greets strategically placed throughout the park grounds. The best way to see if you can catch your favorite characters is to check the Times Guides for the parks when you arrive. If you're staying at a Disney resort, they should have copies, and be happy to give you one. You can also pick these up at multiple areas throughout the park you're visiting...
But if you want to ensure seeing her favorites, I would try a character dining meal. There are 3 princess-themed character dinings: Cinderella's Royal Table at Magic Kingdom, 1900 Park Fare at Grand Floridian resort, and Akershus at Epcot (Norway). To ensure seeing Winnie the Pooh, Tigger, and friends, check out the Crystal Palace at Magic Kingdom (Main Street USA). Not only are you ensured of seeing them, they will walk right up to your table vs. you having to wait in line at a Meet-n-Greet. For example, at breakfast at Cinderella's Royal Table we saw and took pictures with Cinderella, Aurora, Jasmine, Belle, and Snow White. You can still catch Jasmine (with Aladdin) at Epcot in Morocco, and Belle and Beast at France, but again, you'll have to work with the times they're available, plus the lines. If you do try a Meet-N-Greet, however, try to get there a few minutes before the start of the meeting time if you can...
Good Luck! Hopefully your daughter's dreams will come true and she sees all her favorite characters!