In the New Batman Adventures tie-in comics, Barbara Gordon brings up the fanon-until-recently theory that Harley Quinn and Poison Ivy are a couple, to which Harley implies that the Rogues say the same thing about Batgirl and Supergirl… I can see it.

Babs and Kara don’t appear together that often on-screen, but in Justice League they are apparently close enough to spend Christmas together according to the Kents, so yeah.