I want to spoil things about what happened in the original timeline, because goddammit the original Mia deserved to be loved and remembered. I try to avoid spoiling what happened and focus more on her character development
The story in general
The story is about Mia Luna Tearmoon, a dumb, clueless, arrogant, and spoiled princess. A pretty common sight in nobility considering their privileged. She lived her life like the world revolves around her. She acted like a child, doing whatever she liked without thinking of the consequences. But then the world gone to shit.
During this time, Mia did something uncharacteristic of her, she tried her best to do something to make the situation better. Of course at that point it was already a bit too late. Much of the damage was already done, her reputation is ruined, and her lack of studying earlier in her age come back to bite her. Even then, she still tried. Ludwig would sometimes saw Mia walking down the hallway with a notebook filled with a bunch of names of important person on her hand. In her later year, Mia actually grew into a fine leader, still not the best or the wisest leader, but a fine leader Ludwig is proud off.
Mia's final year before execution
In her final year, Ludwig was running around begging to the enemy leaders for Mia to not be executed, or at least talk to her one last time. Because Ludwig knew, yes Mia was dumb, yes she arrogant and spoiled, but she was never evil. Her action cause the suffering and deaths of many people, but none of it was done out of malice. She was willing to admit her mistake and (at least tried to) fix them. And when things went south, she still tried her damnest. While other nobles were running away or hiding in their territory, Mia was still running around the country to try to save it.
But every story needs a villain, and people are determined to make her and the royal family the villain.
After Mia's execution
After Mia's execution, Ludwig disappeared from the world stage. Despite his much needed skill, he just couldn't bring himself to work under someone else anymore. The last time we(the readers) know about him that he was drinking in a bar with his friend, lamenting the fact that no one knew the real Mia was. He chuggs down his wine before singing praise about the hated Princess Mia and starts a bar fight.
This one is just my own addition (not canon) on how Mia escaped. Also spoiler on who is the enemy that executed her.
The reason why Mia could escape when the revolution army was barrelling down on the Capital was none other than Ludwig. While Mia never run away, it doesn't mean she was afraid. When she heard the news of a revolution army coming after her(and the royal family), she was terrified. But she still continue working because she still believe that the Royal Army would beat them back so all she need to do is do her job. At that point the Royal Army was basically non existent, most of the soldiers have run away looking out for themselves and most nobles ignore the call to arm. Maybe she didn't know, maybe she did and was just convincing herself so she doesn't get overwhelmed by fear.
When the revolution army knocked on the door, Ludwig asked Mia "do you want to escape?", and it just broke Mia. So she took the offer and due to Ludwig incredible competency, Mia managed to escape, though not for long.