- "It's not out time, and it's not fair! Not like this!"
- —Mary Jean panicking as they are trapped in the tunnels.[src]
Nothing is known about Mary Jean's life, except for the fact that she is 17 years old and was a student before the outbreak.
Mary Jean is one of the members of Jeremiah's group that get trapped in his Church. After being trapped in the underground tunnels, Mary Jean panics, and is told to shut up by Rose. After being rescued from the herde of walkers by Lilly and the Woodbury survivors, she becomes a member of Woodbury. Jeremiah listed Mary Jean, as being best suited to be part of the foraging team in Woodbury, as he hands Lilly a chart of the members of his groups best attribute, age and occupation. Under the oaks of Woodbury, nearly the entire population gathered, and Mary Jean along with Noelle made extremely strong punch made from canned fruit juice and Ben Buchholz's horribly made moonshine.
After the Church group finally decides to all be part of the mass suicide in Woodbury to join with God, Mary Jean is one of the females of the church group that prepare the sacramental food and drink back in the kitchen. After the idea of taking their lives fails, as Bob switched out the poison with water, Stephen blows the Woodbury gates as part of the plan, to let the undead in. However, as they failed to take their own lives, the Church group scatters as the horde arrives in Woodbury.
After Stephen blows the gates to Woodbury, the undead overrun Woodbury and Mary Jean is devoured by walkers trying to escape.