@Gryphonknight has an excellent (but long) discussion of how to decide what to do with emblems here:
My question for you is: do you mainly use Sonya on offense, defense, or both?
If the answer is offense, then the class talent probably doesn’t help her all that much, but the stat boosts do. Slash attacks and specials against an offense are less frequent than tile damage against a defense, so the short duration of the def boost isn’t super useful.
If you use her on defense, though, she’ll benefit quite a lot from getting emblems.