Does your daughter like video games? Disneyquest is my 9 year old son's FAVORITE thing at WDW. It's like being inside of his biggest fantasy. My 7 year old daughter hates it.
The video games have height requirements, but an average size 9 year old should be able to do everything. They are also very "boy" geared - pirates, space, comic book heroes, and a very intense roller coaster simulator. It's a perfect antidote to all the princess stuff. If you have a kid that is into all the video game stuff - they'll be in heaven. If not, we really enjoy the water parks as an alternative to the main parks.