WARNING: The following contains spoilers for Batman #100, by James Tynion IV, Jorge Jimenez, Tomeu Morey and Clayton Cowles, on sale now.
Over the years, DC has turned Harley Quinn from villain to anti-hero, and as much as it aligns with her cartoon series and the Suicide Squad film franchise, she just feels a bit more virtuous and selfless in the comic pages, especially when in Batman's presence.
It became apparent again as she allied with the Bat-family, feeling like an official member in "Joker War." But as that event concludes in Batman #100, a major change is coming as the jester appears to have been positioned as the Dark Knight's most important protege.
This direction is taken one week after the climactic battle against the Clown Prince of Crime at Ace Chemicals. The Bat chose to run down and save Harley from blowing herself up, leaving Joker and zombie Alfred to explode at the other end. When she recovers in the hospital, Bruce is there, the same way he'd be for a Robin, Nightwing, or a Batgirl. They share a father-daughter moment which really shows how much he considers her an equal and a full-blown hero.
He talks about Gotham's rebirth, as well as his evolution, and indicates it's going to be a new chapter for everyone. He's brutally honest, though, and admits maybe he didn't need to be inspired by the weight of the past -- all the trauma and all the deaths -- and that he has to kill the past to become a new beacon of light. He sounds optimistic and hopeful, not to mention vulnerable, and implies he wants Harley there to help facilitate this change. We haven't seen him open up to anyone like this, not even Damian, except with Alfred, and Harley feels honored to be bonding like this.
Admittedly, she thinks it's weird she and Batman are exchanging pleasantries, but it seems they need each other for the new journey to come, painting a picture similar to Sean Gordon Murphy's Batman: White Knight. Bruce needs more than "yes men" for the job to come and as seen with her wanting to kill the Joker, he does need a foil who won't just follow orders. He requires someone to test, question and keep him in check, which he might not get from the Bat-family as they share a unique DNA, and in Damian's case, blood.
But Harley calls it like it is and she's not bogged down by the Bat-symbol or legacy. This isn't her dynasty so she can call Bruce on his B.S. and make the tough decisions. Not that he'll agree with all, and for sure, some he'll stop as seen when she wanted the clown dead. But still, this pushes Bruce even more to ensure none of his kind, as well as himself, ever steps over that line. And as unconventional as she is, Harley's a reflection of the good and the bad, a reality check that mixes the idealism with the grime of Gotham.
With Joker and Punchline out there still, certainly leveling up, she'll be a key cog if the city's to be protected. She understands the ground, the heartbeat, and the streets of Gotham, and is an unrefined, unpolished sidekick that views things differently than those who trained in the Bat-cave or lived in mansions. Plus, she gives insight Bruce can't get from the others who've lived in the light, not the dark. This can help Bruce with the criminal mind, finding a remedy the others couldn't help him attain, especially as Harley understands therapy and rehabilitation due to her psychiatrist's background. In that sense, she can even help heal Bruce to become a better Batman, while ultimately, bringing him closer to Joker.