Agh, this is SO incredibly cute as I said; the body language is perfect and I just love her expression (poor Applejack). I really hope you might decide to do more with this at some point, but even as a sketch it's great!
she looks like "omg a dog!" or something. pretty hard to see anything she would be afraid of though. maybe she is standing on the edge of a tall building or something, I mean she is an earth pony and all.