Mother Superior is the leader of The Order of St. Teresa.
After Homer leaves Maggie on the doorstep of the church, she takes Maggie in and raises her in the Church. Lisa goes in the church undercover to find Maggie and ends up solving a lot of clues to find out what the gem is. She is told by the Mother Superior that the gem is Maggie, not her, as Lisa thought it was her. Marge then takes Maggie from the Church.