Wow, I called the princess situation totally wrong. I really don't know what to make of her extremely brief presence in the story. A simple, sheltered girl, treated like an object by her father, and forced to kill herself because he was too proud to accept his own defeat? I don't know if the author honestly expects us to be so awed by Pauliana's "kindness" that we don't even question why it was necessary in the first place - the country had already officially surrendered, so why not use the princess as a figurehead to legitimise their dissolution into the empire and smooth over the transition? The author has already skipped over and beautified the vast majority of the war and conquering process, so why go out of their way to include this part?
Not to mention, I'm thoroughly skeptical of the idea that plunging a dagger into your own heart is a quicker and less painful way to die than a cut to a carotid artery. As far as I know, it's true that a person will die significantly faster if their heart is stopped or critically damaged than through loss of blood anywhere else, but the neck is out in the open. You have to cut deeper than you'd think, but you can get there. To reach to her heart, she'd have to pierce her dress, her skin, multiple layers of muscle, the pericardium, and the heart itself, which is a whole ball of muscle. That's going to require a lot of force that a terrified princess will struggle to produce, even with Pauliana's assistance. Not to mention, she's angled the dagger vertically, so even if she can aim for her heart and not just jam the thing into her sternum, she's almost certainly going to have to scrape through her ribs. It looks to be a pretty bad time, is what I'm saying.
All of which is pointless nitpicking, I know, but if you're going to base a scene around your main character "kindly" advising an innocent girl how to kill themselves honourably, you should probably google it first. Or spend a frame to justify it, if absolutely nothing else. In a story so light and fantastical that we just saw an entire country unilaterally surrender based on a jousting tournament (won by a single knight, no less) this feels unnecessarily brutal.