Through her friendship with Katherine Mansfield, Maata (Martha) Mahupuku's name has become known in New Zealand literary circles, but little so far has been recorded of her life. She was born in Greytown, Wairarapa, on 10 April 1890, the daughter of Emily Sexton and her husband, Richard (Tiki) William Mahupuku, a sheepfarmer of Longbush. Richard was the son of Wiremu Hikawera Mahupuku and nephew of Hamuera Tamahau Mahupuku, prominent and wealthy leaders of Ngati Parera and Ngati Hikawera hapu of Ngati Kahungunu. Maata can scarcely have known her father for he died in September 1893. Two years later her mother married again, her second husband being Nathaniel Grace, a sheepfarmer of Gladstone. Maata's half-brother, John, was born in November 1895.
Maata may have attended Gladstone School and by 1899 or 1900 had entered Miss Swainson's Fitzherbert Terrace School, Wellington, where her aunt, Mary Sexton, was a pupil. There she met Kathleen Beauchamp (later known as Katherine Mansfield), with whom she soon became friendly. In 1904 Maata's great-uncle Hamuera Tamahau Mahupuku died, leaving a vast estate which was to be held in trust for Maata. The same year, her stepfather died. In 1916 her mother remarried; her third husband was James Laurenson, an accountant of Carterton. Maata was apparently still in New Zealand in early 1904, but soon after left for Paris to attend a finishing school. There she learned to speak fluent French and developed her talent for singing.
In 1906 she and Katherine Mansfield met in London where Mansfield was attending Queen's College. They decided to keep diaries for each other. One of Maata's was used by Mansfield in an unpublished story, 'Summer Idylle', written in 1906. This was the first of several stories in which Maata appears. Mansfield's friend Ida Baker (better known as 'LM') met Maata in London and was impressed by her beauty and charisma: 'Petite, with a pale touch of gold in her skin and sparks flashing from her eyes, she was a fascinating little being'. Towards the end of that year Maata returned to New Zealand just as it became known that the money held in trust for her had been embezzled by H. S. Izard, a well-known Greytown lawyer. While it is not clear how much, if any, of the money was recovered, Maata retained ownership of considerable areas of land.
Maata Mahupuku, probably feeling unsettled, began to visit her Maori relatives in Wellington. She also had friends in Wanganui where on 10 April 1907 she celebrated her 17th birthday, staying in a hotel. While at Wanganui she kept a journal, which she later gave to Katherine Mansfield, who kept it all her life. The journal contains passing references to Mansfield, but focuses on a love affair with an unnamed man, and reveals Maata's self-assurance at this time: 'How ridiculous it seems to think that I am only 17 – of course le bon Dieu made a mistake and I was born with a brain or mind and it began to develop straight away'.
Mansfield had also returned to New Zealand in late 1906, and until she departed for England in July 1908 regularly met and corresponded with Maata Mahupuku. While her feelings for Maata (or Carlotta, as she sometimes called her) were evidently intense, Maata's interests were probably now centred on George Stewart McGregor, to whom she became engaged in 1907. He was a farmer, son of a well-known Wanganui couple George McGregor and Pura Te Manihera. Maata and George were married in St Luke's Church, Greytown, on 5 December 1907.
For a time they lived in Wanganui where their son Richard was born. Within a few years they had moved to Greytown where two daughters were born: Te Huiaakaka and Te Rereomaki. During this period Maata was an enthusiastic supporter of Liberal politics, as her great uncle Tamahau had been, and was seen driving the Liberal candidate J. T. M. Hornsby around the Wairarapa district in her car during an election campaign.
In 1914 Maata's marriage to George McGregor ended, and at Greytown on 24 October that year she married Thomas Asher, a widower of Maori, Dutch and Jewish descent who owned land in Wairarapa. In 1932, however, that marriage also ended in divorce. There were two daughters, Nani and Patricia (Patsy).
Of her relationship with Katherine Mansfield little more is known. Mansfield continued to think of Maata, and possibly to correspond with her. In 1916 she wrote 'Kezia and Tui', a story apparently based on recollections of her friendship with Maata. After her death in 1923 it emerged that she had begun a novel entitled Maata. This work, while it appears to be autobiographical in origin, describes a situation in which elements of Maata's experience can be detected. A manuscript containing two chapters and a plan for 33 others went on sale in London in 1957 and was later published. Maata Mahupuku claimed that she had in her possession a complete manuscript of the novel, along with many letters from Katherine Mansfield, though she did not make any of this material public.
After residing at Greytown for about 30 years, with a brief period at Wellington, Maata left sometime after 1940. For a while she lived at Bulls as the companion of Rangi Kerehoma, and eventually settled in Palmerston North. She always lived in opulent style, had a passion for elegant clothes, liked jazz and parties and was known to be extravagant. She was also hospitable and generous, with a warm personality. Those who met her in later years described her as a charming, cultured and sophisticated woman.
Maata Mahupuku Asher died in Palmerston North of heart disease on 15 January 1952, aged 61. A son and daughter from her first marriage and two daughters from her second marriage survived her. She was buried in the private burial ground of the Mahupuku family at Kehemane (Tablelands), beyond Martinborough.