I would have excused her rudeness if she was that way to everyone, but given how she address the emperor, it is clear she has control over it. I won't accept the excuse that the emperor can kill her if she's rude, because well, Geralt does exactly that and gets away with it, the emperor is a practical man. He won't do anything as long as he needs her.
When i was rather rude to Emhyr, he told me to not forget with whom i am talking to, but Geralt has also an unique history with Emhyr. Without spoiling anything, Emhyr wouldn't be the same person without Geralt's doing in the books.
As for Yennefer, Emhyr promised her and the other sorcerers of the lodge immunity or at least refuge, if she finds Ciri and bring her back, what she probably never intended to do, but anyway, if your fellow colleagues are being hunted and burned at every corner, you won't bite the last hand you are getting, even if it is a black one.
Just look at Keira, she was so despaired that she even tried her luck with Radovid.
All in all i am not really happy with the situation with the sorcerers in the games, they got screwed way too fast. In the books there was a whole society with schools and even research buildings, but that went all downhill with the witch hunt and it doesn't look like it gets restored anytime,
sigh.
Nothing to do with her per se, but I didn't like the way it she was pushed in the spotlight against the player wishes.
Yeah, CDPR kinda created this self-made problem by doing their own thing, offering/establishing Triss as an alternative, but at the same time they wanted to be faithful to the books. But by doing that they could only satisfy a part of the players, people like me, who never doubted the relationship to Yennefer.
I tried to give my opinion in one of those Triss' threads, maybe to explain why it happened this way, but i kinda fear looking into it again and see the reactions of it...
I have constantly the feeling to be sorry that it happened this way and not different, because if you pursue Yennefer and reaffirm their relationship, it is
exactly how i thought it would be. The only thing i regret is not being able to talk thoroughly with Triss.