She figured out that a clue about someone who couldn't cover their own behind was about Key-san because of his pants! So that means that Key-san and Norma-chan, the one who got the clue, are both sheep!

We could eat them, but I'd rather get rid of the people I know are going to figure us out before I want to get rid of people who just wouldn't tell the other sheep anything by disappearing!

And yes! You can make locked posts to them! But it's probably safer to not do it right away and to only make locked posts to people everyone knows are sheep - like Norma-chan and Key-san - so that it doesn't seem suspicious!