Her mother, the daughter of Vanessa Bell and the painter Duncan Grant, and a niece of the writer Virginia Woolf, was an artist.
Growing up at Hilton Hall, near St Ives in Huntingdonshire, Henrietta and her sisters Amaryllis, Nerissa, and Fanny were all sent to the co-educational Huntingdon Grammar School.
[1] Burgo Partridge died suddenly of heart failure on 7 September 1963, three weeks after the birth of their daughter Sophie Vanessa, leaving his wife a widow at the age of eighteen.
[1] Garnett's cousin Virginia Nicholson later recalled that "Everything about her, from the overpowering scent of Guerlain's L'Heure Bleue over breakfast, to the limitless Gauloises habit; from her deft skill with rough-puff pastry, to her passion for the Victorian novel – exuded fascination.
About early romance, its storyline included incest and suicide, and in the light of the author's Bloomsbury background, readers looked for parallels with real life.
In 2004, she published Anny: A Life of Anne Isabella Thackeray Ritchie, a biography of William Makepeace Thackeray's daughter Anne Ritchie, who was a sister-in-law of Henrietta Garnett's great-grandfather Leslie Stephen, converted into Mrs Hilberry in her great aunt Virginia Woolf's Night and Day.