i think my problem with the manga is that it randomly veers into the kinda mean spiritedness id expect from something much more brutal and dark. there are times where it brushes up to that and i dont mind since it gives the manga teeth, which is something a manga following a relatively well trodden premise needs. but when it goes into complete overkill on the revenge its like our protagonist is a mafia boss (a western mafia boss) where if you've slighted her slightly you'll get gunned down in a dark alleyway somewhere. that kinda revenge fantasy doesn't really work well for most audiences, i mean at least in count de monte christo bro was imprisoned for over a decade while some dude courted his wife and by the time his revenge is complete he contemplates whether he went to far. this bitch gets out of jail in like a week's time and goes on a marry ol adventure. not saying she shouldnt get revenge on her former fiance and break the country that betrayed her but i shouldnt hate her while she does it.
It's a bit more complicated than "my fiance throws me in jail so I'll get revenge on my country".
Elizabeth was educated to become a Queen in every matters (political, wars, governement...), from a young age she took the burden of doing her fiancé's job and letting him get the credit for the job she actually did. The King and the Prime Minister (who's also her father), noticing how good she is in such works put more and more jobs in her hand and let deal with the Prince's wrong doings.
Besides this, she also became an influent marchant to help her finance her charity action for the poor and her citizens. Most of her most trusted allies follows because she did everything in her power to help them, while hardly knowing them (like Mireille). Her company also created many jobs for the citizens in general.
So when she was sent to jail by her own fiance (and they still sent her the job the Prince was supposed to do lol), not only her father and the King didn't do anything to free her from jail, thinking she could figure out a way out herself, she learned the Prince created false accusation to tarnish her popularity in the Kingdom, even worse, the Prime Minister (aka her father) chose to backup the Prince by adding even more false accusations and save the Royal's reputation.
She had many reasons to betray the Kingdom and get revenge, but without Mireille, Elizabeth would still do everything in her power to help the kingdom because she was educated like that.
Also I would like to add something to everybody thinking Ellie
kills children so they're out. They completely forget that before being that, she a kind person who always goes out of her way to help those in need. There's a huge contradiction in her behavior and it will surely backfire at some point.