Seems a good fit, she could use the rage of Joker driving her nutts.
I think besides Batman, Harley Quinn should be the one to kill Joker.

Always imagined her a Violet Lantern. Yeah, Harley or Red Hood should kill him.

I agree that Harley should kill him, but if she ever did it should/would stem from the emotions of grief and resolution. Harley has never been an angry person, and to think that she should be a Red Lantern is, frankly, silly. If she attracted any ring at all, her "ability to feel great love" makes it painfully obvious that she should be a Star Sapphire. In fact, it is an oversight on DC's part to have not at least toyed with the possibility, perhaps in Blackest Night.

Wow, nobody? IS THERE NO ONE TO CHALLENGE ME?! NO ONE AT ALLLLLL?!

Because KurmikVurn is so eager to make me double post, it will even break its own two-post rule.

See this, KurmikVurn? I am your forever superior -- I have posted three times in a row, and you only have yourself to blame.

Saying Harley should kill Joker is like saying Batman should do it. We all want it to happen, but it never will. Unfortunatley, DC is always gonna make Harley crazy over Joker, which is a direction I don't like but I'll have to deal with. That's not pessimism, that's realism. My dream scenario would by Joker doing something really twisted, cruel and evil. Harley tells Joker to stop, and Joker almost beats her to death. Harley snaps and flat out brutalizes Mistah J, and becomes a solo hero untill teaming up with Jason Todd (Which is MUCH better than Harley and Joker IMO)