In a stunning admission from Harley Quinn, the rogue revealed she knew her beloved Joker didn't love her. Despite all the love she sent her "puddin's" way, Quinn knew her feelings would never be reciprocated for one tragic reason.
When Dr. Harleen Quinzel of Arkham Asylum took on the Joker as patient, she almost immediately lost herself to the Clown Prince of Crime's charm and influence. His silver tongue was enough to convince the psychiatrist to abandon her normal life and join him as his partner-in-crime. Having cast all else from her former life aside, Harley Quinn's romance with Joker was everything to her. And while the relationship was far from perfect, it kept Quinn by the villain's side for years, convinced that deep down that Joker loved her as much as she loved him.
And yet, it seems that even when Harley was still in love with the Joker, she knew she was outmatched by something the clown actually cared for. In Harley Quinn #25 by Karl Kesel and Craig Rousseau, Harley is drafted by Batman to help in a way that only she can. The Joker has been missing for weeks, and the Dark Knight uses Harley Quinn to draw him out. However, once Quinn manages to locate her Mr. J, she double crosses Batman and goes along with a plan to feed the hero misinformation straight from the Joker. To send the Dark Knight on a wild goose chase, he sends Harley back with clues in the form of jokes. By the time Batman receives his first one, he can already tell Harley is attempting a diversion to help Joker escape. Harley rebuffs Batman's suspicions, saying the Joker isn't leaving and confides that she thinks the Joker likes Batman more than her.
Joker being in love with Batman would certainly make sense from Harley's point of view. Throughout their entire partnership, Mr. J never showed Harley an ounce of the attention or obsession Joker's spent on the Dark Knight. Even at her most dedicated to Joker it seems that Harley knew she could never gain his favor in the way Batman seemed to be able to. And that realization may have helped Harley break off her obsession for good.
While Harley’s grasp on reality is sometimes a bit questionable, she’s actually quite insightful, owing to her professional career as a psychiatrist. While she may not like it, Harley Quinn knew Joker and Batman had something that she and Joker just didn’t. After all, Joker had been tormenting Batman long before Harley ever entered the picture. Someone as bright as her would have been able to peg that Joker was as obsessed with Batman as Harley was as head-over-heels for Joker. That knowledge no doubt helped Harley eventually break away from the Joker for good, knowing that no matter how she felt, she'd never get the love she put in to their relationship back. Realizing the Joker couldn’t love her back was a stepping stone Harley Quinn needed to form her own path.