Also why is the king here?
That proves how stupid the princely couple was. This is the king's birthday party, of course he would show up.
(Note: that could have been a public celebration or holiday, but consider that it's a nobility event where his son was present. His presence should be expected.)
They were so set of following the script that they didn't even bother to realize what happens when you change the setting from "graduation party" to "king's birthday party".
And that's before you even consider that the king had this planned to catch them making a huge political blunder.
That was probably the "heroine" speaking, though it was a bit ambiguous, so her own delusions are partially at fault. It still underlines how unprepared she was. Though she was an evil schemer, she wasn't cunning enough to keep her composure in public and arrange events that fit her plans.
That said, the second part of the chapter is so sweet it nearly gave me diabetes.
Way to go, Rufus. Though you come out as a bit overpossessive at times, you also seem to be a considerate husband. Delicate balance to achieve, so do your best.