Not really a complaint...

I play and generally get murdered by anyone with high mobility. The way she kills people is by throwing her Q on them then spamming E. If she misses Q (that circle on the ground that explodes and poisons) she won't do any damage nor will she get the bonus movement speed she needs. The backup plan for missing Q is to W but that can only be placed far away from her. If you play an assassin champion like you can avoid her Q with his Q by leaping onto her. This also puts you out of range of her W making her completely helpless.

Also she has no escape and falls off hard if she gets behind in gold. Ask your jungler to kill her a couple times early game and you should do fine.

Honestly? I just play Ahri into her.

I mean, I play Ahri into most champions. But she feels like she'd be fairly effective into her even if I didn't main Ahri.

You don't really beat Cass by counterpicking her, you beat her by dodging her Q, faking out her ult, respecting her level 2 kill pressure, and out-roaming her. Her waveclear is pretty poor early on, so anyone who can push hard is a good choice. is fairly safe in this regard. A good would probably be tough for her as well since you can sustain through her harass and pool to avoid her ult.

No u.