From a New York Times obit by Richard Sandomir headlined “Nancy Mitford, Biographer of Zelfa Fitzgerald, Dies at 84”:

Nancy Milford, the biographer of women who helped light up the Jazz Age — Zelda Fitzgerald, the “original flapper” and wife and literary muse of F. Scott Fitzgerald, and the poet Edna St. Vincent Millay — died at her home in Manhattan….

An indefatigable researcher, Ms. Milford brought the chaotic, troubled Zelda Fitzgerald and her world to vivid life in “Zelda” (1970) through letters, albums, scrapbooks, interviews with her friends and her husband’s as well as reports by psychiatrists who treated Zelda for schizophrenia. Her mental health was declining by the late 1920s and led to institutionalizations in the 1930s and ’40s.