Mistress 9 is going to be a while writing so for a mini special let us look at a wide range of princesses and see how well they rule starting with the most recent anime I watched, Cautious Hero.

I'm being very generous with Rosalie's picture as this is her at her best, she doesn't really deserve it though.
Rosalie is Gaeabrande's princess, daughter of the veteran king dubbed the Warmaster. Growing up with such a known hero gave young Rosalie a strong sense of justice which she uses to motivate her army in defeating the legions of the Demon King, only problem is her head strong determination gets most of her army butchered, it's a trait that I expect from a poorly written Dynasty Warriors character not a monarch in a fantasy anime.
And while yes, doing nothing just prolongs the bloodshed on innocent people but blindly going into battle without a strategy wastes soldiers lives, call Seiya unheroic as much as you want, but his actions saved way more lives and took out way more enemies than Rosalie ever did. It's any wonder she got slapped so many times before stepping back.
After all "What can you protect when feelings are the only weapons you have?" - Kira Yamato