@2dKnight: Actually, this character originally had a white shirt, but I changed it to black because I thought it fit her personality better.  That said, I agree that she could use more contrast.

Experiment with black outlines:

Not sure if this looks better, but it certainly makes her more visible against certain backgrounds.

Experiments with shirt colors:

Meet Nina the platform game heroine.  Age 16, ethnicity Arab, wears blue jeans and a black tank top, wields a scimitar.  C&C welcome as always.

The window spacing looks weird, especially on the buildings in the background.  (Are those points of lights even supposed to be windows?)

General rules for window spacing:
  - Buildings are divided into storeys/floors.  These tend to be of a uniform size past the ground floor.  Windows rarely cross over between storeys, so they tend to be aligned more horizontally than vertically.
  - The bigger the building, the more of its surface is covered with windows.
  - Floors will look smaller on buildings further away, but the decrease is gradual.
  - The tallest building in the world has 163 floors.  Don't go any higher than that if you want a realistic, present-day setting.

Also, I think you could strengthen the overall impression of the picture by darkening all colors except the yellow and adding a bit of blur around the yellow, like this:

(I cheated and used a filter for the blur.)

I actually like the more subtle motions of your first attempt better than the more exaggerated motion of your second attempt.  The timing is definitely better in attempts 2 and 3 though.

Is this the player character for a platform game?  If so, you may want to nix the anticipation frame(s) and launch the character directly into the air.  I'd rather have responsive controls than ultra-smooth animation.

Added some more animation to the hair.  The effect is rather subtle.  Maybe too subtle.