
It's bcs the repeated assassination attempts came from his own country. The crown princess *understandably* want jesse to come back as he is her lil bro, but his friends and colleagues want him to be safe. Jesse current friends wont take any gamble on his safety, wondering wether the sis is in hostile camp or not.
And the sis can't just eliminate her father (the consort that order for jesse's assassination) as she somehow respect him, thus her dilemma from earlier chapter.

It's the fact that his sibling is a crown princess, the heiress, the next in line, where her stance is ambiguous towards the assassination act (in their eyes), and a really strong knight at that. Putting them in a room together, alone, would compromise jesse safety.
The kingdom sees elisier as a crown princess first before a sister to jesse.
These ppl are the real villains not letting siblings have their reunion even for a bit. This proves that they still think of his as a hostage, always locking him up in his room.
I feel a bit relieved at the end when pink hair tries to comfort the crown princess, but then angry again bc they ALL knew the crown princess just wanted to TALK with her BROTHER.