As far as I know, Appies have great dispositions, but I just wanted to say that the temperment of the breed, or even the individual horse, can't guarantee that you or your daughter won't get hurt. You can have the best horse in the world and accidents can still happen because they are 1000 lb prey animals that can get scared and panic. And even if they don't panic and you just fall off from lack of balance, you are still a good distance from the ground.
And all horses are individuals too. So I wouldn't worry so much about wether Appaloosas as a breed have good dispositions, but just work with your horse as an individual and see how it goes, always being careful because your daughter is still young for a horse of any breed/size and it is a long way from the ground. So have fun, but keep safety foremost.