A combination of this and Tear Jerker: In one issue she dies and goes to Hell, which is sad by itself as while she's a villain, she's still someone the reader has come to like and care about, plus it's not really her fault she's a psycho to begin with. At one point she is basically put in solitary confinement for whats implied to be quite some time (as time is different in Hell than on Earth). It doesn't completely break her spirits, as she says she's still with someone she loves: herself.
The reason she gets kicked out of Hell is also pretty sweet: she is just too upbeat and cheerful and it's threatening to ruin the ambience of gloom and despair the demons try to keep.
Harley becomes pretty much a superhero as she decides to no longer want to do anything with the Joker and though she has moments of being Ax-Crazy she does keep herself in control as when she was being too loud while watching a movie and a couple of people tells her she is being too loud, she agrees with them and apologies for it, she is now friendly, nice, sweet and kind towards people after she goes solo.
In issue #2, Harley and Poison Ivy free all the animals in an animal shelter that permits euthanization and turn Harley's studio into an indoor park to keep them there.
In issue #25 Harley meets the Joker again but however instead of letting him control her again she rejects him making it clear that she is done with him for good which also shows unlike all the other times that she comes back to him despite how he treated her, she clearly has changed for the better and after dealing with him goes back to her friends also showing that she has indeed moved on from him and found people who care about her and who she also care about as well in return knowing that they care about her and love her also as well unlike the Joker.
Harley gives Big Tony the last love berry from Ivy's plant to help him win back his girlfriend Queenie on Valentine's Day. Sure, it does backfire (because the berries are loaded with pheromones), but you can't say she was trying to screw him over considering the idea was helping him get together with Queenie.
The fact that Ivy has left Harley some medicinal plants at her apartment. The signs on them show that they can cure pains and upset stomachs. In fact, most of Harley and Ivy's interactions are pretty sweet.
Harley meets Bruce Timm and Paul Dini, her literal creators, at Comic-Con.
Harley meets a beluga whale. Much cuteness ensues.
Harley will, from time to time, team up with or run into various superheroes through variously contrived circumstances (the list includes Power Girl, Wonder Woman, Batman, and Green Lantern). At least most of the time, the heroes compliment her on trying to do good, even if the results of her efforts vary.
Harley gets a new job as a psychiatrist after moving in but she puts makeup on as her skin is permanently white after being put in a chemical tank thanks to the Joker and despite her insanity does genuinely care about her patients as after hearing from one of her own that her family doesnt see her often Harley is not happy about it and confronts her family but however as she was about to drown them her son tells her that his mom has Alzheimers which causes Harley to realize her mistake so she frees the son who was about to rescue them but however it turn out to be low tide so there was no risk for them to be drowned after all but the point still stands as Harley shows herself to be a good hearted woman who does the right thing in her own way and she will apologise to anyone who turn out to be innocent she has done wrong to.
In Red Hood and the Outlaws, Red Hood/Jason Todd mentions that he underwent therapy sessions at Arkham, and that Harley was in fact his doctor, and that her treatment was something he took to heart and he uses it to calm down a new Bizarro after he and Artemis Grace find the big guy in Black Mask's HQ. It further proves that for all of her rather glaring faults, it proves Harley is different from the Joker, being that she had a positive impact on one of his most prominent victims.