Well, it sounds like your personal feelings are what's driving you to defend her here, exactly because you know people like her in real life. I certainly hope you're not making excuses for them as well though, because those kinds of people hurt others for real, not in a fictional setting.
I personally don't subscribe to the reasoning that good traits can excuse having a horrible side. If a world renown surgeon saves thousands of lives in his job, but turns out to be a pedophile and child rapist, does that make him a good person ? It is an extreme example, not meant to be a complete parallel, but Quinn is doing harm one way or another.
There's a saying that every villain is the hero of their own story, and while she may not be on the extreme end of things, she's definitely not a good person. Everyone has an excuse or reasons for their behavior, but a line has to be drawn somewhere as to what's acceptable and what's not.