Nancy Hartley works as a maid in the Harrington household, reporting to the stern Aunt Polly. She joined the staff approximately two months before Pollyanna Whittier, her employer's orphaned niece, arrived in Beldingsville. Nancy becomes the first person to befriend Pollyanna upon her arrival, forging a significant bond that bridges their differing social statuses. This friendship leads her to help Pollyanna adjust to her new life and navigate Aunt Polly's strict rules.

She embodies warmth, compassion, and a strong sense of duty, demonstrating empathy in her interactions with Pollyanna and offering emotional support as the girl contends with Aunt Polly's initial coldness. However, Pollyanna's energetic and unconventional nature often overwhelms her, clashing with the household's expectations of propriety. Nancy conscientiously adheres to social norms and rules in her duties, yet occasionally faces reprimands for perceived lapses in attention or efficiency.

Over time, she evolves from a cautious employee into a more assertive advocate for Pollyanna's well-being. This shift is evident during key moments, such as preparing the attic room for Pollyanna despite Aunt Polly's initial reluctance to make the child comfortable. Her loyalty drives her to mediate between Pollyanna and Aunt Polly, trying to bridge their differences while upholding her professional role. Her supportive nature is further highlighted when she remains actively involved in Pollyanna's care following the girl's accident and during her recovery.

Beyond her work, she enjoys playing the piano and storytelling. These skills bring moments of joy to the community, as she sometimes entertains local children with her tales. Her personality blends a sense of responsibility with creative expression.

Her relationship with Aunt Polly is complex, balancing professional obedience with quiet resilience. While she initially struggles to meet her employer's exacting standards, her consistent efforts reflect her commitment to the role. Simultaneously, her nurturing kindness deepens through her growing bond with Pollyanna. She has brown hair and black eyes. Her role remains consistent as a supporting figure whose development centers on increasing protective instincts and emotional investment in Pollyanna's happiness, without direct involvement in plotlines extending beyond the Harrington household.