I think your contact frame is the main problem. There should be one frame where her heel is just touching the ground, but the weight is not yet on it. Then in the next frame, all of her weight is on that leg, and it is bent. The difference between those two frames will give the animation some weight, which it seems to currently lack. Right now, once her leg touches the ground it never looks like any weight is put on it, just like she glides over it.
Other then that, her legs snap back too much, kind of like she is trying to kick up some dirt behind her. Just alter the frame where her leg is far back, and it will be alright.
Also, try and get a good pendular movement going with her arms. They snap around too much right now.
Keep up the good work.