Responses
I just think that she is still a little girl. Gurl keep on pushing the brothers to FL ( it is obviously that FL doesn’t want anything to do with her brother) that is why I find her annoying. If she is mentally an adult she should know how to set boundaries. That’s what I’m thinking. Besides from that nothing else.

I hope the black haired guy isn't the ml. He was engaged to her, the bare minimum would be treating her like a person, not a wall, even if was political and when it's convenient to him because he now catched feelings for her, he's trying to care. How about apologizing first? You are aware about how high society is, so of course you know she would be mocked and humiliated if you ignored her.
I think it's just that you want to save your petty pride and go for marriage thinking it's a appropriate "reward". I need him to understand that she does not need to forgive him and he should not expecting to be forgiven and to be treated 'well' when he does not even apologize.
I also think the lil' sis is kinda annoying too. What do you mean "I'll do my best, so please don't abandon my brothers"? The ones that have to do their best are they, can't they think and reflect for themselves? Also, they abandoned her first so why shouldn't she 'abandon' your brothers? They never had a good relationship in first place, they let her be ridiculed by their own servants.
Hope she realizes that by saying that, she's ignoring the suffering the princess was passing through and passing a hand on the head of those who are wrong aka her brothers. They had no business being so rude to her ヽ(`Д´)ノ