Sheila DeMars is a woman who works at a Christian church, which is the rival church of Eileen's Catholic church. The two of them have a burning hatred for each other. Every Christmas, her choir always one ups her choir. She appeared in the episodes The Real Christmas and The Real Brother's Keeper.
In the episode The Real Christmas, Sheila and Eileen got into a fight over who would win the church choir battle of the bands. Eileen sent Jimmy to spy on them, but he got caught and recieved no footage. In the end, neither of them won.
In the episode The Real Brother's Keeper, the two of them stopped fighting and become friends. It was revealed that the reason for their rivalry in the first place was not because of their differences in religion, but because Eileen stole her parking space one time.