Never thought of her as evil,she`s not,just look at all the"she CAN do that,she MIGHT do this..." and so on,it`s all imagination.
She`s more of a Catwoman type of gal,a bit of good a bit of bad
Ms. Kyle would, eventually, help someone just because, hell, even Dr. Isley helped her fellow dr. just because, Quinn is yet to do this.
Judging solely by what's been shown, I see Quinn much more as a Joker (Hamill, not Ledger or Phoenix), she's sadistic and manipulative, she knows it and she loves it; she can and does plan, but not as masterfully as she beleives and relies heavilly on improvising, which she seems to be good at.
Makes a great villan and a awful Ms. 88, but hey, it's ur popsicle that will or not turn yellow and fall off, I won't tell you where to put it.