Winner of the "Tranquility Lane Finest Meat Pie" award three years running, Mabel is suitably proud of her (delicious) accomplishment, and her hobby allows her to listen in and chat with all manner of friends and neighbors. No secret is safe with her around!
Like the other inhabitants of Vault 112, she is trapped in the Tranquility Lane simulation by Stanislaus Braun.
Tranquility Lane: Mabel is one of the residents you will have to kill if you choose to do all of Betty's tasks. If you killed Mabel before Braun gives you a request to kill her in a "creative" way, she will respawn.