I really think she might be an appaloosa or part appaloosa outcrop. Lift up her tail and check her udder - if the skin is mottled she probably is. And if she's smarter than the rest of the horses and harder to get along with, she definately is. :)
What do you mean by mottled? In my area that's blue:'( She's very smart but easy going but has her days like most women:')