Don't tell me she didn't know that was rude to say about the duchess. To me it's a clear diversion from the talk about consorts that get thrown out. She just uses the dumb and innocent act because it's been what's effective for her so far.
Also I think our eyes are going to roll right out of our head seeing how the Emperor still wants Navier to show him affection/be affectionate with her when he straight up brought another woman home whose every action works to humiliate or annoy Navier. Even if he doesn't blame Rashta, he knows the Navier doesn't welcome her presence. I can get him finding Navier a bit outwardly cold and wanting more affection, but that's something you sit down and talk out with her. Any expectation of that goes out the window when he starts outsourcing. The audacity of him saying Rashta is cute and fun but he feels comfortable with Navier - ick, if Rashta is trash, he's the rotten odor clinging to it.