
I agree for the most part. The only thing is that I believe that there is a mistreatment from the ML. On the early chapters, the ML keeps on dragging the wedding, if someone asked when will they wed he gives vague answers even though it was already dragged. Like, the the wedding should be after her birthday, then ML went to war, and I forgot the others. I think it's already mistreatment since he keeps on dragging it and even said in his monologue that he doesn't want to marry FL. And we know that age matters for women to be wed at the right time in these historical scenes.

I also agree for the most part. I think her wanting to leave him is understandable bc from her perspective their love is doomed and she will end up dying no matter what she chooses. The book show the routes with her and the ML hasnt been working out for her so i get that shed rather remove herself from the situation then keep on trying for something that isnt guaranteed.

I do think on the whole it was the wrong decision on his part, but it wasn't out of cruelty or condescension towards the fl. He was simply too caught up in his own notions of the kind of marriage he wanted vs what he thought he will get with the FL. So he chose to stall for time instead, putting off making a decision. Remember, him breaking off the engagement would make her the object of ridicule, and make it much harder to find another match in the time period the story is set.
He didn't see how his actions could hurt the FL, he didn't see how that could be perceived as indifference by the FL. It was his ignorance, not mistreatment, and he is now taking steps to correct his mistake by inviting the FL and trying to salvage the relationship. That is why I root for him.
At this moment, due to her preoccupation with the book, the FL is also hurting the ML. He is being honest with her, and confessing he likes her and wants to keep the engagement. But she keeps shutting him down and pushing him away. And actively pushing her towards maria while dancing with the prince. So she is also tunnel-visioning like he used to, and is now hurting him in the process.
Side note: I love both the ML and FL. I'm seriously rooting for both of them.

You got a point but age matters a lot in these times. Another is that FL wasn't trying to make the ML fall for her, and she didn't feel like the ML could protect her. She gave her word that she wanted to break the engagement but the ML didn't want to. Of course she would push him away, and she didn't pull back. Did she?? (I forgot)( ̄∇ ̄")

Rather than ignorance, i think what affects the most in this case was his indifference. His "couldn't be bothered to care" attitude was what most readers resent the most and the FL also lowkey resents that.
I get this feeling that what hits the FL most is how no matter what his love turns away from her the moment she dies (i think, this is speculation) Like, ofcourse we understand the complexity of grief but let's put it like this: He wants a loving marriage but she won't be the only love till his grave while he will be hers, and being told that over and over most absolutely suck, the FL is too kind hearted to resent the "culprit" of her death and doesn't truly hate that she will be the same woman to then continue to build a life with HER (FL) love of her life... And neither does she resent the ML for moving on after her death,, it leaves this 'how unfair!' bittersweet feel on the reader because the ML truly doesn't see the vastness of her love and kidness, (yet) that is what i think also makes it more rewarding to read " i can't wait until he sees it!! " i keep thinking (∩´﹏`∩)
The crown prince is still a sleaze hitting on an engaged woman repeatedly. And the FL is really unconcerned about the ML, trying to pawn him off without explanation. I guess he deserves to suffer a little for judging her before and not making an effort towards their engagement, but that doesn't make him the worst ML that the FL must leave. In fact, the FL can be accused of behaving the same as the ML used to, right now.
Both of the leads are flawed and more self-centered, but that keeps the story interesting, and it makes sense for both FL and ML to behave this way. The only people I dislike in this story are the redhead and crown prince, both of whom keep trying to hit on the leads despite knowing they are engaged.
I don't understand this expectation from readers that the ML has to be absolutely perfect and someone who unquestioningly worships the ground the FL walks on. He is allowed to make mistakes, have flaws and still be a compelling character who we root for. The ML hasn't mistreated the FL, she has just read in a book the the ML will betray her in the future. He is carrying the blame for a crime he hasn't committed.