Sister Winifred Callahan is a nun at Jane and Frankie's old catholic school who used to scare Jane as a child, describing her as "the meanest person" she has ever met her whole life. Sister Winifred was awarded a federal grant at the Boston Police Department to counsel families of homicide victims. Although she preferred Cambridge, she lost the grant to a Sister Helen-Marie.
- In a deleted scene from Money Maker, Sister Winifred revealed to Maura that her father, Patrick Doyle, was one of the students in the first class she ever taught. She had thought of Paddy as "FFA" (a future felon of America) because of his Irish mob family but also recognized his gifts. She offered to show Maura his record but took it back when she saw Paddy's drawing of her as Maura was looking through the file.