My DD is now 9, but she was 8 in April when we last went. The main things at each park are based on what you/she want to see. I'd start with buying a Disney for Kids book and have her look through it making marks on the things she wants to see. The check out allears.net or the disney website with her so she can see a glimpse. If it's a surprise here's the attractions that my DD9 says are must dos:
Epcot - we eat around the world - literaly. We start at Mexico and grab a small something from each country. At the same time they get to learn something about each country with the Kidcot locations - kinda too old for it, but DD9 liked coloring the mask and collecting the tags from the CMs. On the rides - Spaceship Earth, Test Track (a must), Soarin, Universe of Energy (if it's running). In Japan you can pick an oyster for $14 and they will take out a real cultured pearl that you get to keep. Watching Miyuki (a Japanese candy artist from Tokyo) is amazing and sometimes you get picked for the free candy. Turtle talk with Crush at the living seas, Journey into Imagination with Figment and there's some fun games at Innoventions. The Garden Grill at the Land is a nice place for dinner/lunch or Restaurant Marrakesh at Morocco (Moroccan cuisine and belly dancers)
Animal Kingdom - we don't spend a full day here. We do the Tough to be a bug at the Tree of Life, Festival of the Lion King (a must for our family) at Camp Minnie-Mickey, Kilimanjaro Safari at Africa, Kali River Rapids and Jungle Trek at Asia, the Boneyard and Finding Nemo-the Musical (a must for us) at Dinoland. I usually don't plan on having dinner there and honestly we've only made the Jammin Jungle Parade once or twice.
Studios - Beauty and the Beast show is like a broadway show and she'll love it. If she's adventureous and likes roller coaster rides (and you do too) there's Rock n Roller Coaster - DD9 hated it - she actually got sick on it so I'd pass it if you don't want to. Honey I shrunk the kids is fun, unless she's afraid of snakes or lions. Muppet Vision 3D is always fun. Make sure you get a temporary tattoo at the fountain - they're only $5 or so and they'll last the entire trip. If you allow those things. The toy story mania is new and suppose to be like a carnival game. Voyage of Little Mermaid is a nice sit down show to slow things down. Hollywood & Vine (buffet) or Prime Time Cafe (1950s home cook meal) are good places for dinner. Gertie the big green dinosaur has some yummie ice cream you should grab around 2:30 and then find a seat in front of the big hat for the 3pm parade. There's a High School Musical 2 parade the comes out - check your schedule.
Magic Kingdom - Honestly this depends on how much your little one is still a princess!! We always head back to Fantasyland - Cinderella's carosuel and I make sure she rides the one horse with the golden ribbon in it's tail - that's Cinderella's official horse. Then it's off to the small world, winnie the pooh, peter pan, snow white we see Ariel over at her Grotto and Storytime with Belle (check your schedule). You can book a special hair style - princess or diva style at the Bibbidi Bobbidi Boutique at Cinderella's castle. Adventureland - Pirates of the caribbean and magic carpets. Frontierland - Big thunder mountain, splash mountain (if she is up for these types of rides) and country bear jamboree. Liberty Square - Haunted Mansion. Mickey's Toontown - Barnstormer (again only if she's up for it), Hall of Fame/Judge's Tent to see the princesses. Tomorrowland - buzz Lightyear, space mountain (only if she's up for it) Indy speedway, monster inc laugh floor, Carousel of Progress (my DD loves to see how people lived 'in the old days'

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So I hope this helps and isn't too long. If you have any questions PM me! We've gone to Disney a lot so at this time DD9 can give people directions - we never carry a map. She'll be honest about what she likes and doesn't like.