When Jaxx said she was infected and had to be put down, he just wanted to kill her. The madness in his bright eyes allowed no argument. He threatened to shoot anyone who disagreed and leave them for the Walkers.
I felt sorry for the nameless girl who crossed paths with our supply run and expected us to save her. Instead, Jaxx did ... things. He always was a twisted bastard. Not one of us, but she deserved better. He had known her before, unlucky enough to meet again in less civilized times.