zuko has a lasso from morla that makes anything obedient to him -- and the jabberwock is no exception! he can make it sit, etc. so, he'll definitely want to assist grell there if he knows she can actually touch it! he's wanting to calm it down, but if he finds out the jabberwock killed the dragons of the world, there's a good chance he'll want to put it down instead. (he has a dragon, he doesn't want druk to die. ;_;) but i think he'll be able to help her out wrt getting ON the jabberwock since he can probably literally make it sit.