All I know is that she's the deputy director of the information and publicity branch of the WPK. That's a pretty influential post in any ML organisation.

But at lot of this "ruthless sister dictator" thing came from Americans staring vacantly at pictures and guessing. She is thinner and less smiley than her brother, so American Hollywood trope brain immediately went "she's cold, calculating and evil".

We probably have a resident DPRK expert in here somewhere, but if not it might be a nice hobby to develop. Consider starting at the WPK newspaper: http://www.rodong.rep.kp/en/