Rehutai Maihi was the elder of two daughters of Te Paea Nehua and her husband, Nētana (Nathan) Maihi, a bushman descended from Ngāpuhi leader Patuone. She was born on 16 September 1895 at Whakapara, near Whāngārei. Her father died when she was young, and after her mother's second marriage, to Weretā Ārama (Adams), she gained two half-sisters and a half-brother. The family was Anglican, and Rehutai attended Queen Victoria School for Māori Girls, probably for two years, enrolling in 1911. She was good at sports, including golf, tennis and horse-riding, and was an accomplished pianist and vocalist.
Rehutai Maihi trained as a compositor for the newspaper printing trade in Whāngārei and later Kaitāia, and soon moved into journalism. She acted on several occasions as editor of the Northlander newspaper during the 1920s while its owner, Allen Bell, was in Parliament. She also wrote for the Kawakawa Luminary, and the Northland Age, becoming well known in the north under the pen-name 'Nellie Nathan'.
In June 1932, with approval from Whāngārei elders, she launched a Māori-language newspaper, Aotearoa. She invited contributions and included the text of the Treaty of Waitangi in the first issue. Aotearoa was unusual at the time because unlike other Māori-language newspapers it was not supported by one of the established churches. It was printed in the office of the Mirror, a short-lived Whāngārei newspaper for which she was then working. She described herself as 'editor and publisher', using the names Rehutai Nētana and Nell Rehutai Nathan. Aotearoa began as a weekly, but issues became less frequent. By December 1932 Rehutai was producing it at Whakapara, in smaller format, with a press she claimed was used for the Treaty of Waitangi. The newspaper temporarily ceased publication about mid 1933. On 13 November that year she married Stanley Gilberd, a divorced 43-year-old boring contractor, at Ruawai. They had one child, a daughter.
In 1935, using her birth name, Rehutai Maihi was a candidate for the Northern Māori electorate, the first Māori woman to stand for Parliament. Her high lineage allowed her to do so, and also enabled her to speak in the course of her campaign, notwithstanding the conservatism of the elders. At all places she was 'accorded a very good reception' and her meetings were well attended. She stood as an independent, describing her policy for Māori as similar to that of the New Zealand Labour Party; she was particularly interested in the welfare of Māori women and children, and the employment of boys and girls just out of school. However, the overwhelming support for the eventual winner, Tau Hēnare (Coalition), and his rival, Paraire Paikea (Rātana), made it difficult for her to gain a following and she came sixth of the seven candidates, with 156 votes.
In September 1940, while living in Kaikohe, she resurrected Aotearoa. Realising that with the onset of war the men overseas would be hungry for a newspaper in their own language, she commented on the progress of the war, as well as reporting local events of interest to Māori readers. Publication was at first fortnightly but later monthly. This time Aotearoa lasted for over five years, the last-known issue being 1 November 1945, but it was never a commercial success.
By the mid 1940s Rehutai's health was poor, undermined by undiagnosed diabetes. Nevertheless, she remained a member of the Māori Women's Institute, and was a staunch supporter of the Māori Women's Welfare League, travelling to some of its conferences. She spent the last years of her life at Kaikohe. Her husband died in April 1967 and she survived him by only a few months. Her death occurred on 12 August at Bay of Islands Hospital, Kawakawa.
Rehutai Maihi seems to have been frustrated by not being able to use her many talents and skills to the full. Fluent in Māori and English, she 'had very definite views and had the education and background to put them across – or at least fight hard for their adoption'. While she may not always have achieved her aims, through her persistence she not only stood for Parliament but maintained on her own a Māori-language newspaper. Well known and respected among Māori and Pākehā, she was rightly remembered as 'a busy wheel'.