Angelica Garnett: Painter and writer who grew up in the dysfunctional Bloomsbury set

Presence and magnetism: Garnett at her home in Forcalquier, France in 2007 (ANNE-CHRISTINE POUJOULAT/AFP/GETTY IMAGES)

Shortly after Angelica Bell was born on Christmas Day 1918, David Garnett wrote to Lytton Strachey about the baby, "I think of marrying it. When she is 20, I shall be 46 – will it be scandalous?" In 1942, following the death of his first wife, "Bunny" Garnett did indeed marry her. The disparity in age was the least of the complications.

Angelica was the daughter of the Bloomsbury painter, Vanessa Bell, who was married to Clive, the celebrated art critic, by whom she had two sons, Julian and Quentin. Though Clive continued to stay on, at least for the weekends, at Charleston, the Sussex farmhouse they leased from the Gage estate, their marriage had amiably fizzled out. Vanessa had a lover, Angelica's father, the predominantly gay painter Duncan Grant. As conscientious objectors during the war, Grant and Garnett were working as agricultural workers there. Bunny was also Duncan's lover, and would have been Vanessa's as well had she not ruled out the ménage à trois as an unorthodoxy too far.

Despite the premium the Bloomsbury set attached to truth-telling, as Angelica revealed in her acerbic memoir, Deceived with Kindness (which won the 1985 JR Ackerley prize for autobiography), she was allowed to believe Clive was her father until she was 18. This is only the beginning of the tangled family tree.

Angelica and Bunny had four daughters before they parted in 1967, Amaryllis, Henrietta and the twins Nerissa and Fanny. In 1962, the very young Henrietta married Lytton Burgo Partridge, the son of Frances Marshall Partridge, sister of Bunny's first wife. Burgo died three weeks after the birth of their daughter, Sophie. So Angelica and Frances were the maternal and paternal grandmothers, while Bunny was both grandfather and, by marriage, great-uncle to the child.

This leaves out of the account Angelica's tender relationship with her aunt, Virginia Woolf, and uncle Leonard; her intense relationship with her half-brother ( she was brought up as his full sister), Julian Bell; her grief after his death as an ambulance driver in the Spanish Civil War; her subsequent relations with her remaining brother, Quentin, and his wife, Olivier; and with Clive and his mistress, Mary Hutchinson.

Bloomsbury life was not simple, and Angelica, in her memoir, and in a set of lightly fictionalised stories, The Unspoken Truth (2010), made it clear she had not forgiven what she saw as Vanessa's duplicity; or Duncan, Bunny and even Clive's connivance at the fib about her father – which might have been to prevent servants' gossip or, more likely, to prevent the Bell grandparents removing their subsidy of the family.

Almost as bad was her mother's attitude to educating her. When you think about Aunt Virginia's grudge regarding her own lack of formal education, it seems remarkable that none of the family injected discipline into what seemed an idyllic childhood in Sussex, London and Cassis in France. In 1928 she was sent to boarding school in Essex, leaving at 16 without any qualifications but with a taste and talent for music (she played the violin well) and an interest in the theatre. At 18 she was sent to live with a family in Paris. She described this exquisitely in one of the tales in The Unspoken Truth.

In 1936 she went to the London Theatre Studio to study acting, but realised she was more interested in the visual arts: painting, but also the Bloomsbury-encouraged arts of illustration and decorating. She attended the Euston Road School where, she said, William Coldstream was good to her but Victor Pasmore reduced her to tears for failing to "come up to his standards."

It was not long after this that she began the affair with Garnett. It is hard to grasp now, but he was then one of the best known of the "Bloomsberries", celebrated as a novelist, editor and publisher. Vanessa was edgy about it, but no one told Angelica that Bunny and her father had been lovers.

"I was wrong to marry someone so much older than me and someone so connected with my parents," she later reflected, saying that she thought the same at the time and still felt guilty about it. The couple lived at Hilton Hall in Cambridgeshire, a beautiful Jacobean house which I remember as being even harder to heat than Charleston.

Angelica continued to paint, worked with mosaics, designed some good book jackets and textiles, decorated pots and in the1980s took up constructed sculpture, using found objects. But in the mid-1960s, after 25 years of marriage, she left the now ageing but mellowed Bunny, and set up her own household in Islington. Bunny moved to France.

The death of Amaryllis in 1973 was a particularly hard blow, because she had drowned in shallow water in the Thames. Bunny had a houseboat moored on Cheyne Walk, and it was never determined whether she had slipped on the gangplank or was a suicide. Angelica moved back to Charleston after Duncan's death in 1978, and there suffered a severe depression herself.

She worked hard to preserve Charleston and launch the Trust that opens it to the public. She found the self-confidence to go to America to give fund-raising lectures, and was astounded that her audiences sometimes behaved as though they were in the divine presence; it was the height of Bloomsbury-philia. She bought a house near Charleston, at Ringmer, but came to rest for the last 30 years in Provence, at Forcalquier. She had a great deal of presence and magnetism, a beautiful low speaking voice reminiscent of that of Virginia Woolf, and was seldom without male company. She was a green-fingered gardener and a very good cook.

In 1994 she gave her 8,000-item archive, including sketches and drawings by Duncan and Vanessa, to the Charleston Trust; and her own memories of the house were vital to the restoration project. But her greatest contribution was her 1984 memoir, Deceived with Kindness. It was written with, and in pain. The facts it revealed reflected poorly on all Bloomsbury.

Angelica Bell, artist and writer: born Charleston, Sussex 25 December 1918; married 1942 David Garnett (two daughters, and two daughters deceased); died France 4 May 2012.