In The walking dead box set, after decimating many of Woodbury's caged-up zombies, Michonne pulled her sword on the Governor and then pleaded with Andrea to leave Woodbury. When the pair feared being denied freedom, Merle opened up the doors for them, ensuring Andrea would want to stay. Knowing this was the Governor's plan all along, Michonne decided to defy him and actually leave. And then the Governor dispath three guys to kill Michonne.