Tbf he was already looking at the white haired princess so the only way I could see this situation panning out as it did is that he saw something that was or looked like she was cheating (which is weird cus her maid and the sister still think she’s madly in love with him so why would she cheat) and decided to give her the cold shoulder and was interested or pretended to be interested in white hair to make her more jealous and fawn over him more. Then she pulls a reverse uno and decides she’s done with him and moves to the guy which makes him desperate.
Actually read some spoilers and he walked in on her kissing another guy just to make him jealous how else is he supposed to percieve violet kissing another guy??
I Dont get too much of her hostility if she's the one that cheated and then acted like the bitter woman. I dont care too much for the Duke but she acts like the violet from the story was miss perfectly in love and just got ditched and trashed. Not saying she should get with him but she should look at both sides and fix her attitude.