Subtle works, a light touch, perhaps a bit of dry wit - certainly language acknowledging the Evil Evil nature of this Kitten will always be the most "effective".

Scots Gaelic. Simple answer.

French. I love it when my partner whispers something in a naughty voice in french!!

Maybe if you just "purrred" at her?

do you think that it is the language that makes it sexy or your partner speaking it?