I like the story. Names are entertaining if not hard to read. Got a little bored with the endless chapters focused around the Questioning, though I get why you chose to write it that way. Where it is a dull affair, might I recommend you add some extra humor? You did a little, however, its length requires more to keep the reader engaged. A dull scene can be immensely entertaining. Keep in mind that boredom leads to chaos. If you center the event around the chaos you accomplish your goal and keep your readers invested. Overall, the story is good and I like your style. I look forward to seeing where you take it.
Read the story now
If you will allow I have a few editorial suggestions.
For the Questioning, Fifi could make up amusing nicknames for them based on their appearances. There could be more unrestricted internal dialogue in response to answers. This is where she can make fun of them without consequence. Was his reply absurd or did it have little merit? Would it be deal breaker for her sister, or her? Where is the guy is from? Is it a nice place to visit, or somewhere the princess would never want to go? Does he belong or stand out among his people in attitude, looks, or hygiene? Are there any know conflicts in the region? Is he the reason for the conflict? How do his answers compared to what she knows? If Minne has any nervous habits this is a great time to present them, even if only her sister picks up on it. Fifi is an artist, so she might look around for inspiration, or focus on the pin at his lapel as something she could draw or critique.
Don't forget about the little brother. As a member of the royal family, he needs a bigger presence. That does not mean you have to add more scenes with him in it, however, a twelve-year boy, even a prince, is not just going to sit ideally by and watch his sister interview over two dozen suitors, no matter how well behaved he might be. You already said he would be outside practicing for hours, so he much prefers movement. He will get restless and fidget, maybe voice opinions, even if his father steps in to quiet him. Being a boy, and the heir to the throne, he has more freedom to express himself. This can be shown here. As his parents sit regally, he could be picking his nose, eating cakes, or melting into his chair about to doze off as his sister asks the next useless suitor her list of queries. Fifi could sit there watching him, wishing she was fortunate enough to be afforded such liberties. How the prince acts in these scenes as opposed to the princesses can show a great deal about the different ways they base roles on gender. It also adds the chance for Fifi to express any feelings she has towards her brother or the way they are treated, you can even do this when introducing him. When the eldest prince agrees to help him with swordsmanship there should be a time mentioned for it to occur, or a way for the princess to know it has occurred, so it makes sense when she brings it up while dancing with him at the ball. Furthermore, the ball scene should have a moment or mention where the young prince is dancing or snacking before dropping off to sleep. If you add these, it will give the story more life.