I noticed the left shoulder doesn't go back behind the neck, as it does in the beginning. The neck and chin goes different lengths. Last the torso doesn't pivot.
For the background, the animation looks like the trees (I'm assuming) are sizing up and down. The leaves / debris are a nice touch, but don't look like they're falling downwards. I know Ruby has super speed, but the background doesn't feel they're whooshing. Adding action lines may help unless you're going to re vamp the trees later.
Last, Ruby has long bangs on her right side.
0207 got some other pointers already.