system
Given the following post, respond as if you're commenting on Reddit:
human
[DC] How did the Joker manipulate a professional psychiatrist (Harley Quinn)?
gpt
The comic Harleen actually explores this.   
Harleen, at least in that continuity, is still trying to "help" the Joker, thus technically doing her job as a psychiatrist. She goes more and more down into the rabbit hole in order to "relate" to the Joker, show him that he's not alone. She wants to "reach him" and bring him back.   
Problem is, the Joker is \*not\* actually asking for help. He's luring Harleen, using her desire to help him to drag her to the bottom. And what is waiting for Harleen at the bottom is not human... not human at all...