She always had the group's best intentions in mind, in my opinion. She was a friend and I don't betray friends, even when they're wrong. That was more than enough reason for me to let her stay. Not to mention that everybody knew what she'd been through the last week and yet, nobody cared. Especially Kenny.
She was the only one to find there was a traitor and she was right. Why on earth would I abondon such a person. Even if she wasn't a friend, she was like one of the most valuable people in our group. I would've ran away with her if the game allowed me to.