@RamenRider it was not about dumping responsibility. Do you even read? The reason why she was executed? The kind of person she was before and how she acted? Do you think that the masses cared about, oh even she was a royal but she was just still kid? No!!
I don't read the novel or raw, so my knowledge is as far as the chapter in the manga. Do you even read this chapter? The beginning of why the trio hated Mia? Selfish, ignorant, stupid.. someone who doesn't befit to rule. But then, Mia didn't change. Until the day of uprising, she was still that selfish foolish princess.
Like I said, it was the duty of a royal to be an example for the subjects. Mia? She didn't clear her name, she didn't care about the incident because it didn't concern her. She throw her responsibility away! She didn't have to act actively in the government, but if she investigated or ordered an investigation about the incident, and acted accordingly befitting that of an imperial princess, the opinion of the trio wouldn't be so low. It was precisely because she had power, chance, and influence to do so but did nothing, as in nothing, that made her as guilty as her family members. The kind that indulged themselves in their selfishness and didn't care a bit wether their people were suffering or not.
As Mia once confronted by Ludwig about the royal family's spending on food, she didn't know the answer.
My suggestion, reread again, don't skim, the you know why Mia was as guilty as the other royal families. And that is exactly as I've said, she was selfish and ignorant. Instead took chances and learn, she didn't care at all.
Yes, Mia now is still the same. The difference is now she acted as if she cared so that people misunderstand her intention. But well, maybe the saying is true. Action speaks louder than words.