Appaloosa's, like any horse breed, can be mean, pig headed horses if bred for color instead of for temperament and conformation FIRST and FOREMOST.
A big issue is that people pick the prettiest, or best looking Appy's, and give no thought to their actual quality as a breeding horse.
Bad training can also cause meanness and stubbornness. Your girl was obviously trained well.
Does she have papers? Appaloosa's are sometimes born solid, or with a light color light her you may not be able to see her color. Some Appy's have thin or scraggly mains/tails, and some may have fuller ones. She could be an Appy cross if her mane and tail are very full and long.
Wait! I'll fix it....