Hi, Maria! There are several rides and attractions that have height requirements. For safety reasons, you will find that things like Tower of Terror, Splash Mountain, and Expedition Everest all have restrictions forbidding people under a certain height to ride.
I don't know how tall your daughter is, but if you go to
www.wdwinfo.com and do a search for "height", you can put her height in the calculator, and it will give you the list of rides and attractions for which she would be too small.
Even with height restrictions in place on some rides and attractions, there is so much to do at Walt Disney World, I'm confident that she won't feel like she is missing anything. My three year old doesn't even mind when her big sisters go on something without her, because there is usually something interesting for her to do while we wait!