That's the double edged sword of the whole thing. Just because we can accept the reasons behind someone's actions, doesn't mean we can excuse the actions.
There's a friend of my family that has diagnosed mental problems and it makes them a bit of a cunt from time-to-time, and I tried to explain to my twelve year old daughter that it wasn't this person's fault they are a cunt, to which she replied, "but they're still a cunt." I might be slightly paraphrasing my kid's words here...
But with Quinn, and with anyone who doesn't have a physical impediment making it impossible for them to change, there can always be a path to redemption. It just comes down to whether you can be fucked putting in the effort to help them get there.
Will Quinn find her path?