having mental condition of narcissism and doing behavior like a princess.
if she has 공주병, she does as very arrogant way as if she was a princess.
Literally 공주병 is Princess sickness.
Definition by other languages (含义 / significado / परिभाषा / 意味 / Bedeutung / définition / 뜻)
자신이 마치 공주인것처럼 거만하고, 자기애적으로 행동하는 심리상태. (korean)
영희는 공주병 말기환자 같이 너무 거만해.