Jeannetta Margaret Walker was born in London, England, on 19 June 1864 to Anne Jane Randall and her husband, Alexander Walker, a printer. Her father, a Scot, held his country's system of education in high regard and when Jeannetta was six he sent her to the esteemed Mary Erskine School. She graduated in 1881 having passed the university examinations in English literature, history, geography and French, and was also qualified to teach junior German and drawing.
Jeannetta became a governess, first in Balmacara, Ross-shire, and four years later in Edinburgh. While there she contracted typhoid fever and to aid her recuperation visited relatives in Dunedin, New Zealand, in late 1887. Supported by her Edinburgh recommendations and a letter from a family friend, John Hislop, former New Zealand secretary of education, Jeannetta found work as a governess in Dunedin, and later on a country station at Dipton, Southland. Here she enjoyed the social life of a rural community as she participated in their concerts, dances, picnics and hunts and shared in the combined Anglican and Presbyterian worship.
On 12 April 1893 at Dunedin, Jeannetta Walker married James Blackie, the Presbyterian minister of the Dipton–Taringatura parish. They had two daughters before James Blackie died on 22 November 1897 after a short illness. Faced with supporting her daughters, Jeannetta Blackie settled in Queenstown and by 1900 she had opened a small private school.
The Presbytery of Dunedin considered Jeannetta Blackie's educational qualifications, organisational experience and commitment to foreign missions as ideal for the position of superintendent of the new Presbyterian Women's Training Institute in Dunedin; the few deaconesses already working in New Zealand had been trained in Australia. In taking up the appointment in June 1903 she became the first woman to hold an official administrative position within the Presbyterian Church of New Zealand. Working in conjunction with a small committee she administered and supervised a residential deaconess training programme for women planning to enter foreign missionary work.
From the outset it was difficult to sustain the institute. To keep costs to a minimum Presbyterian Theological College lecturers and other professionals offered their services on a voluntary basis, and the domestic upkeep of the institute became a requirement of the practical course, which on occasions caused tension among the students. The greatest obstacle that Jeannetta Blackie and the committee had to overcome was the opposition of the wider Presbyterian membership to women being trained as official church workers. Her patient perseverance won through, however, and by 1912 the Presbyterian Women's Missionary Union undertook an information campaign to raise funds for a new building to accommodate the trainees.
During the difficult years of the First World War, when fewer women offered themselves for deaconess work, Jeannetta Blackie's skilful administration helped to secure their position. She implemented a number of projects, from a form of trade aid selling oriental goods, to opening the boarding facilities of the institute to high school and university students. Personally she made many sacrifices, for instance refusing to accept an increase to her £45 annual salary. On her retirement at the close of 1918 the Presbyterian Women's Training Institute was well established with a firm network of support. She had seen its quarters grow from a small home to a building of good size, free of debt and with assets totalling £2,500.
During the 16 years Jeannetta Blackie was superintendent, 60 women trained as deaconesses. She demanded from them a high standard of commitment, perseverance and courage and took a keen interest in their individual careers. These women served in India, China, South America and the Pacific islands, as well as in New Zealand. She had undertaken a difficult task with no traditions on which to build and retired at a time when a new approach was required in the worldwide Christian missionary movement. Although struggling with partial blindness, Jeannetta Blackie continued her association with the missionary union and was a loyal member of Knox Church. She died at Dunedin on 4 May 1955 survived by her two daughters.