From skimming through it.
It's because Elizabeth is still in the game-mindset. She thought that the prince's yandere mode was a result of misunderstanding Leonid's "she's mine" line at the party(press F for Leonid), and some other reasoning that was related to the game's events.
But essentially, she think that he's only yandere from some triggers, not that it's his natural state (at the end she's like "staaaahp don't fall (into yandere)!" when the prince started showing some 'darkness' seeing her and Leonid 'flirt'.
And I think the queen found out between ch 16 and 17, since at the start of 17 she's trying to apologize for the prince's action (she brought him along because he said there's someone he's interested in there, but she didn't expect him to go this far)
On one hand, the prince seem to be out of the picture for now with ch 17, on the other hand, a new smug guy appear.