I like it actually, but heres some things....
That are good and that can be improved:
-Posture & Anatomy:
She looks like she is in a rather uncomfortable turned position of the head, and her shoulders look as though they might be a bit to far back for the way that she is turning, or rather bring her right arm around more to the front to give her a more "I'm running, aren't i cute" kind of look.
Her mouth looks a tad to high, and her jawline seems a bit to rounded, maybe add some small detail marks and shading to give the jaw a bit more depth.
Other than that the rest of the body looks pretty good overall.
-Background & Scenery:
The sky has a nice subtle but effective feel to it. The detail to the plants is actually quite nicely done. Maybe a touch of shading on the grass and the other plants around the grass. Also make it look as though it is flowing along with the (what appear to be) leaves flowing in the wind, by having the grass bend in a similar direction, but without making them look exactly the same.
The floating "leaves" look a bit to out of place as far as the detail goes, but would look nice with a bit more color and shade.
And well, the ground looks like it is either sand, or dirt, it is to hard to tell. Practice a bit more on ground styles cause along with the rest of what is a pretty good looking picture, it is a bit of a distraction rather than a nice detail.
Hopefully i wasn't to harsh on you, i actually really liked it, even with it's minor flaws! =3