I guess to me, the idea that the Spirit World would suddenly abandon the Avatar without warning and choose a new emissary to the world is more of a conspiracy theory than the idea that Amon is puffing up his credentials. 

Watching the scene, it also seems less like she's hoisting the guy off the ground cold, and more using his own momentum and her cloth thing to swing him around off the ground.  I can buy it from a very strong young woman who's very advanced in martial arts.

SPOILERS

(STILL WITH THE SPOILERS)

Rebuttal from myself as a pre-teen girl: Oded Fehr.