There is a need for more tension when she's in the backflip state and she sticks her sword in the ground. Maybe another keyframe with only slight movement, to show she is straining to pull off the rest of the move. In theory it would add a presence of gravity to the animation, though i am by no means a master of the animated gif.
+ framerate displays differently between mozilla and internet explorer, etc... so someone watching this in a different browser may be basing a critique on something they are viewing differently than you, in regards to the timing, anyway.
++ this reminds me of Blood : The Last Vampire.