Everything from the pose, to the colours, to the way you drew her hair is perfect. Particularly the hair, which is one of the more convincing efforts I've seen to transfer her highly stylized haircut from the show into something that follows how human hair works. (Even if it is pretty stylized in its own right.) And...
...OH MY GOD! YOU ACTUALLY GAVE HER A PROPERLY DRAWN STETSON!? EEEEEEEEEEEE!!!
Indeed they are, as I can attest to having spent many hours trying to learn how to draw them. Which makes it all the more awesome that you put the effort into actually drawing one instead of copying how the hat looks in the show. (Which outside of the show style just looks wrong.)
Applejack strikes me as the kind of girl who, if human, would not think of herself as pretty. Nor would she be the kind of girl others would notice.
But I think I'd have a liking for her. I've always admired girls who are willing to do the heavy lifting, and I must say you've made her rather attractive here. Although I doubt she'd be the kind to show-off her midriff like that.