There's a difference between being absolute cancer to play against, making everyone else's experience less fun, and making you want to throw your keyboard at a wall, and being "overpowered."
She's the first one. Not the second.
She's an unhealthy champion with a toxic skill set that makes playing against her an awful experience.
But as far as power, she's either average or slightly strong. She's not broken or OP, she doesn't need massive sweeping nerfs. She doesn't need 10000 posts saying how OP she is.
She needs some serious attention as to why she's so terrible to play against, and why the community largely hates having her in a game.
She ruins the game, period. Has nothing to do with her power, and everything to do with her kit being cancer.
Stop saying she's OP. She has average to below average win rates across all elos. She has average or comparable damage to other burst mages. She has counterplay. She has weaknesses (Malzahar, just to name one)
It just doesn't feel good to play against her. It's a total headache that detracts from the overall experience of the game.
She needs rework, not nerfs.