Katsuyu can liquefy itself. Physical attacks mean nothing.If it does go through, it'd tear chunks out of her. And depending on the size of the particular Katsuyu, if it's a breakaway from a larger one, it's potentially over for that Katsuyu.
Though in the end, like I said, it's the regenerator vs the untouchable. It's too hard to tell who'd win and it'd most likely end in a draw of some sort.
Manda can't kill Katsuyu while Katsuyu can kill Manda.
And that was just a 10% Katsuyu, imagine if it were the full slug.