Warner was born on April 16, 1890, in Putnam, Connecticut, to Edgar Morris Warner and Jane Elizabeth (Carpenter) Warner. Her family included an older sister, Frances, and a younger brother, John. Her middle name of Chandler came from her mother's ancestors, the Chandlers, who had settled in nearby Woodstock, CT in 1686. Her father Edgar Warner had graduated from Harvard Law School in 1872 and practiced law in Putnam, CT. The Warners’ house on Main Street was located across from the railroad station.