believe it or not, some people are born evil they don't need a reason to do bad things.
han chae hee is simply a psychopath, she has exhibits all the special traits: charming, arrogance, manipulative, lack of empathy, deceit, no remorse, etc.
and her ability to communicate and control ghosts just enabling her to satisfy her psychopathic purposes.
Oh definitely. I think so too but I'm just giving into the possibility of maybe she's being controlled, still won't make me like her even if that was the case tho.
There has been no evidence so far that's showing she is being "controlled" by someone or something. If anything, evidences mounting she is the puppet master by manipulating people who wants power (Choi Kyung Joon, her right hand old man, and countless ghosts).
I don't think the ancient ghost controlling her, if that's what you're trying to reach here. In my opinion, in the story they are shown as partners to achieve each other's objectives.
The ancient ghost somehow is very interested in Lee Nok, which is why Han Chae Hee targeted him as sacrifice for the ancient ghost. And in return, the ghost provided Han Chae Hee protection and ability to yield her spiritual powers to kill other people and to defend herself from Jaeshin's attacks.
I feel like she was desperate for something and made a deal with a supernatural being that altered her soul into darkness, but damn she's a real villan