This is a good shot! You must be a natural. The picture has so much feeling, it's beautiful to look at, and makes me happy. Is the horse's name "Pippen"? Reminds me of Lord of the Rings. If it were my picture, one thing I might have done is straightening the horizon line (maybe, maybe not, sometimes I like them not straight). Congratulations!
You capture a lot of fun here! I like how there is space in front of the girl--it kind of indicates that she has space to run. The pony's rear end would be nice to include in the picture. Very nice work!
I can see what you were trying to capture and it really works. My few nitpicks are: I do wish she wasn't wearing the tye-dye, it's just distracts me and I wish I could see the emotion on the girl's face. Nice job.