Well, Sabia could accuse the catgirls of spying and suggest to the orcs to either make sure that the catgirls have no stamina left at the end of the day or just be more forceful to them. With this Sabia would throw the argument Bris made back at her: even if Sabia didn't have enough evidence, the orcs wouldn't mind the suggestion and since they are not ready to leave yet the catgirls would just end up more abused if Bris spoke up.One of the simplest yet crude methods: Tell the Orcs to call her Fluffy. She really doesn't like to be called Fluffy when she spoke with Elmy at the bar and Sabia (depending on the players' choice) decided to eavesdrop on them.
Don't know if that's powerful enough to keep Bris on the leash, but at least Sabia can use the nickname for a while.
It would be funny in my opinion, since Sabia knows the catgirls are spying. She told them to do so, but if Bris outs her real identity, then a bit of information gathering couldn't make things any worse for Sabia than it already is. Sabia would essentially say that if she is taken down, then the catgirls will suffer with her so Bris' hands would be tied. Maybe literally too.
Simple, short and works. A better story teller than me could turn something like this into a fun scenario.
But it's interesting that both you and Dante477 considered the possibility of Neve being the source so likely. I didn't play the game you mentioned, but i just never thought of this option. I'll definitely play with this thought later.