What's the difference between Harley Quinn and Duela Dent?

[DCCoolness]

How different is Duela Dent from Harley? I don't know much about her. Is she just another "Joker-obsessed, murdering, crazy chick"?

[Doctor Bifrost]

It's complicated.... The original Duela Dent was a fairly light-hearted character who claimed to want to help out Batman and Robin (particularly Robin), and called herself "the Joker's Daughter," "Penguin's Daughter," and other names, and claimed to be the daughter of various different Batman villains at different times. Robin finally deduced she was Two-Face's daughter. (She did use the name "Harlequin" at one time.)

The character went through a number of transformations and retcons over time, being recreated as schizophrenic, from another dimension, and other versions. She was a member of the Teen Titans at one point.

In The New 52, there is a character who calls herself The Joker's Daughter. She is a psychotic, violent young woman obsessed with the Joker, and wears the face he had removed as a mask over her own face. She has fought Batman, belongs to the New Suicide Squad, and, I think, gotten connected with Jason Todd. I do not know if she has ever been identified with the name "Duela Dent."

In any case, she is completely different from Harley Quinn - Dr. Harleen Frances Quinzel, M.D., a psychiatrist who fell in love with the Joker while treating him at Arkham Asylum, put on a costume, and basically became his sidekick. Her complicated story continues from there.

This might help: https://en.wikipedia.org/wiki/Duela_Dent.