Yes, I see that. He did that last night too, telling her flat out not to talk game alone, without him and then getting upset when he found out she spoke to Dom earlier about the Veto. But Danielle was in the room with them at the time and agreed with Brandon, telling Rachel the same thing.
And Shelli and Jordan also told Rachel the same thing. "Keep your mouth shut."
I'm not saying B may be or may not be abusive outside the house, but telling her not to talk game is in fact the right thing for him to do, if he wants her to win the game.
She may think it's condescending, and it is, but her mouth was her undoing last year and will be again this year. Brendon knows that. Her only chance of winning is for her to keep quiet.