...haven't you noticed? let me spell it out:
a. she sent TS on a quest to fight the spirit of chaos when she clearly knows she can do it herself (screw elements of harmony).
b. she then tells TS to go to a forgotten empire on the verge of collapse and defeat their public enemy #1 BY HERSELF!
I could on, but I won't...
(moral of the story: celestia is to TS as king garon is to Corrin! :(