Even though her actions are annoying now, it's not like the Duke is not at fault either. Ripley is stupid but the Duke is purposely being cruel. Not only did she tell him she didn't want to marry him in the beginning but he also threatened to straight up execute her. It could just be a scare tactic but considering that he's, y'know, the duke and she's only the daughter of a count, it's reasonable for her to be scared.
In the end, she gets what she was aiming for in the first place but she's grown to care for him. He's not exactly an ideal guy personality-wise considering he just completely ignores her very obvious signs of discomfort. It goes to the point she thinks that faking a serious injury might get her out of it and then he's mad because she was lying to him about her injuries? For trying to get away from him?
Yes, she's in the wrong too for being ignorant, avoiding clear communication and having no awareness but I feel as if the duke, who is in a position of power and abuses said power, is far worse than she is.