I use her in UNM UK in relentless set, due to her passives of 20% extra damage to bosses and 10% chance for extra turn + her a3 gives another extra turn, she does get those rather often. Probably one of few chars where relentless set actually makes sense to use.
Though it really depends on your setup, she provides weakness, which I did not have before, as well as I don't have increase attack, so with her self buffs she does similiar damage to Ninja, lagging a bit behind, with them both having pretty similiar gear.
This is in middle game, I do about 60 to 65mil per key and recently stopped relying on poisons.
Of course if you have something like Draco or Jintoro or mass increase attack, then she wouldn't really be worth it.