Here we have Gianna and the now Queen Rosalyn dancing together after the hours of a masked ball that Rosalyn ran to help get the nearby nobles off of their troubles for a night.
Gianna came in secret because of her past (Rosalyn's father had her put to death over her relationship with the then-princess) and disguised herself as one of the castle's servants for this opportunity to meet with the woman she loves. And after the official ball, when the other nobles are asleep or returning to their manors, Gianna takes the queen into a dance, a moment to reminisce of when back as children first discovering their attractions, they would dance with each other secretively in the ballroom. This is indeed a happy moment, but not quite a happy ending. Oh not yet.
After all, there are still the responsibilities of a queen to contend with, and Rosalyn needs an heir at some point, which requires marriage to a king. (And before anyone asks why she doesn't change the law, bear in mind the kind of public outcry the changes to longstanding policies can incite in the real world, and then apply them to less enlightened times to figure out the issue with that).
Can a forbidden relationship both remain a secret and be stable enough to deal with all of that?