Who is Mrs. Carpentier (Sarah) from Mrs. Mike the Story of Katherine Mary Flannigan and what is their importance?

Mrs. Carpentier (Sarah) is the full-blooded Cree Indian woman, who is an experienced midwife that delivers both of Katherine's children. After Mary Aroon is born, Katherine asks Mrs. Carpentier if she can call her Sarah, reminiscent of the Sarah in the Bible, who was the mother to a race. Katherine thinks of Sarah as a fairy godmother even after visiting Sarah's dark and dusty workroom which looks and smells of decay.