The mc just knows that the duke dislikes her but doesn’t know he dislikes her because the duke thinks she’s part of the plan to blackmail him into a marriage basically. Cause he only knows her as the daughter the count is taking care of, not abusing. It’s only when he learns about the abuse that he starts to open up to liking her. Mc just thinks he dislikes her, but then her opinion starts to slowly change later on in the story. She’s had enough of being in a family that doesn’t love her since her past life so she didn’t want to get married to a man who despised her(her opinion changes later). The mc’s plan in the first place was to get money to escape the count’s family in the first place, so it wasn’t like she didn’t have a plan. She just didn’t want to make any attachments to the people at the duke’s residence if she was going to leave in the first place(especially because she didn’t want to hurt Lucius), however her opinion changes when Lucius got sick in the rain for her. She then does decide to get into a contract marriage with divorce in mind and decides to fix anything and treat Lucius well before divorcing.
Also, if she wants to work for her own money, that’s her choice. She might not want to be in a loveless marriage, even if she gets riches. She doesn’t have the guarantee that the ml will fall for her
I'm 4 chapters in and it makes no sense why she would want an annulment. She says the Duke despises her, but it sounds like he despises the dad because he was using a secret against him. Also the Duke seems like a caring individual so he wouldn't mistreat her when they're married. If she doesn't get married to him then she's stuck in the family that neglects and abuses her. Who will then just toss her to the next highest bidder for her to wed. And if she runs then she's going to have to work to make money. I feel like it's poor writing, it would have made more sense for her just to continue with the marriage to the Duke and work with him and treat the boy with care.