Need two animations to be converted...

[Kosheh]

Just throwing out some C&C ~

See Itachi's kick animation that you posted originally?
You might also want to consider having her extend her leg out similar to Itachi's (lean back, kicking out and top leg should meet top of waist) I assume that a martial artist would want to do so to get additional height on the kick (as trying to do the same from a upright position wouldn't allow you to even kick to your waist in the first place. >>

Try drawing a stick figure doing Toph's kick, and how that stick figure could look more powerful delivering that kick (it'll probably look similar to Itachi's)
Then just use that drawing as a template for what you want to do. :V
You might MIGHT have to redraw Toph's body in that animation cycle to make it work (but such is the plight of making custom sheets)

Then there's that motion blur, which is an animation technique that implies the kick is not only strong but that it's also quick enough to be not seen by the human eye, sort of like what you did with the punch.

(okay the real reason is that it also saves frames and makes the kick actually look much smoother when animated)