I personally think that Harley should be the one Batman villainess with zero interest in Batman and without any sexual tension with him. Whereas Catwoman and Talia love him, Poison Ivy is physically attracted to him, Harley just finds him a bore.
She doesn't even share the obsession with him that Joker does. She just helps him in his schemes to kill him because she thinks that when Batman's out of the picture, Joker will finally give her attention.
And Batman likewise has no attraction to Harley. He thinks she's just a dumb psycho.