I dont think she is op. She is balanced in a really unbalanced sort of way. By that i mean, her strenghts are op, but her weaknesses are waaay under powered. Her main strength really is her ult. That's what defines her. All her other skills are technically crap compared to other meele champs. She's like a weaker version of xin or irelia, except she doesnt have a stun/interrupt.

The fact that Reposte can ONLY block basic attacks makes it fairly useless against 95% of champs. You can't block skill shots from panth or nidalee for example, and most ap champs can harass her all day long. Her E is nice for farming and pushing lanes, and her Q is good to chase down enemies with (particularly since you can reuse it a second time) but over all its just her ult that makes her seem OP. And even that is pretty useless until late game when you're running IE at lv 3.

I also find her passive to be god awful. Early game you get such little sustain that even a line of minions will bring you down if you dont have any of your minions to hide behind. I haven't tried stacking bloodthirsters with her yet, so maybe that will offset it, but i find her early game to be way shitty right now. You can either go for early damage, but lag behind in movement speed and atk speed (which really makes that early damage useless cuz you arent hitting fast enough to duel properly) or you can build atk speed and delay getting your atk dmg items till late-mid game.

Im still trying to find a good balance, but she definitely is fun to play if only cuz of her ult. I've had games where i've gone 11/2 and games where i've gone 0/7 so it all depends on team composition.