Harley and Ivy
Well yes, of course they are. But although giving comic characters a homosexual subtext is somehow a whole lot less controversial when they are female rather than if they are male, it's still problematic to openly admit it, especially when the relationship comes out of a cartoon aimed at a 'family' audience, ie. one where the older members of the family don't want to have to explain any of the more complicated aspects of life to the younger ones because the show they are watching was realistic enough to contain any. So although Harley and Ivy are often seen living together, in situations and states of undress that a pair of male characters could never get away with, no details are ever given about their relationship.
Except for one time, in the Batgirl Adventures special, Paul Dini (responsible for the whole situation in the first place) manages to slip in a couple of references that really leave no doubt as to what's going on. The most significant piece of dialogue comes when Harley and Batgirl find Ivy tied up, and at the mercy of the evil Kit Nozawa and her all girl gang and Batgirl says "Why you care about that walking waste dump is beyond me. You'd be safer around a spitting cobra."
And if that wasn't enough, there's also the panel where Ivy describes Harley as "More important to me than you'll ever know." And then when Harley and Ivy are finally reunited...
Aw, it's so sweet.
It's kinda funny that all this paranoid editorial self censorship has actually resulted in a relatively subtle depiction of a lesbian relationship. If they have to pretend it's not there it can never become an issue in the way overt depictions of homosexuality are usually handled.
Go Paul Dini!