Jennie Harrington Whittier, known in life as Jenny, was the deceased mother of Pollyanna and elder sister of Polly Harrington. She married Reverend John Whittier against her wealthy family's vehement objections due to his limited financial means, causing permanent estrangement. Despite this disapproval, their union flourished with profound mutual affection and happiness.

Jennie relocated with her husband to an unspecified small Western American town where he served as pastor. Illness claimed her life when Pollyanna was approximately four years old. Her husband died four years later, orphaning their daughter.

In youth, Jennie surpassed her sister Polly in popularity and accomplishments, embodying a supportive and admired elder sibling. Her compassionate nature manifested in rescuing stray animals, reflecting kindness toward all living beings. Though estranged, her enduring affection for her sisters inspired naming her daughter "Pollyanna"—a fusion of "Polly" and "Anna."

Jennie's legacy permeates the narrative through family bonds and memories. The estrangement from her marriage shapes Aunt Polly's initial coldness toward Pollyanna, while Jennie's defiance underscores themes of love versus duty. Her character functions as a catalyst for these dynamics rather than undergoing active development within the story.