Nancy, employed by Aunt Polly as a maid in the Harrington household before Pollyanna's arrival, initially displays nervousness around her strict employer but finds the niece peculiar due to the child's unyielding cheerfulness amid adversity. She gradually grows fond of Pollyanna, evolving into one of her primary confidantes within the home.

Nancy actively mediates communication between Pollyanna and Aunt Polly, especially when the child's unconventional actions cause friction—such as advocating to keep stray animals against Aunt Polly's rules. She adopts Pollyanna's "Glad Game" philosophy, experiencing a personal shift toward positivity through their bond. Her commitment solidifies through a specific promise to support and protect the child, reflecting deepening nurturing instincts.

Following Pollyanna's accident-induced temporary paralysis, Nancy provides steadfast emotional support and helps sustain the child's spirits during recovery. She persistently champions Pollyanna within the household structure, particularly when the child's optimism falters. Nancy's development culminates in a sustained, supportive role throughout Pollyanna's convalescence and adaptation to Beldingsville.