@deleted user I don't find it to be a bad writing. They want to show how the Empress is only bulling the Duchess behind closed doors. Most of those places you said are public places.
The Empress is shown to be a silent bullie, with the reputation of a Saint, she's annoying but not stupid enough to say all of those things where people can hear.
Her tea time is her safe place, you can't even see the maids when they're together. Without saying, doing the same things every time is a way to show she does that because she can get away with this behavior.
The point is: their only way to break the loop is to show others or even the Emperor her true face, but the Duchess don't want to start a conflict with her, because she knows the Emperor can become really tyrannical because of the Empress.
The Empress is shown to be a silent bullie, with the reputation of a Saint, she's annoying but not stupid enough to say all of those things where people can hear.
Her tea time is her safe place, you can't even see the maids when they're together. Without saying, doing the same things every time is a way to show she does that because she can get away with this behavior.
The point is: their only way to break the loop is to show others or even the Emperor her true face, but the Duchess don't want to start a conflict with her, because she knows the Emperor can become really tyrannical because of the Empress.