Isabella Coupar (the second name, Flora, was added later) was born at Ninewells near Dundee, Angus, Scotland, probably in 1842 or 1843, the daughter of Margaret Mitchell, a jute spinner, and Robert Coupar. Her mother claimed to be related to Dame Nellie Melba (who was born Helen Porter Mitchell). After what she later regarded as a deficient education, Isabella is said to have travelled for some time with her brother in a theatrical company. According to the same account, she then worked in the marmalade factory of James Keiller and Son in Dundee. By 1868 she was working as a jute power-loom weaver.
On 14 February 1868, in Dundee, she married James Cruikshank, a railway shunter, but he died on 12 May 1870 after being accidentally crushed between two railway wagons. It is said there were two children of the marriage, both of whom died in infancy. In December 1870, Isabella Cruikshank set out for New Zealand as an assisted immigrant – one of a group of single women who were brought to the colony at this time to be domestic servants. She departed from Gravesend on the sailing ship England, arriving at Wellington on 19 March 1871. It appears, from passenger lists, that her employment in New Zealand had been arranged in advance. From Wellington, she travelled to Napier on the steamer Rangatira and went straight into service at George Hunter's station at Porangahau.
On 20 May 1872 at Porangahau Isabella Cruikshank married William Jacob Siteman, a bullock-team driver who owned 10 acres of land. He had emigrated to New Zealand from Nova Scotia. In 1887 the couple took up a lease on an Education Endowment block of 233 acres in the Wimbledon district. At first they lived in a rough hut while they cleared and broke in their land. They later built a new home for themselves and one for William's brother, Thomas, who arrived from Nova Scotia with his family around 1900.
Through years of hard work they increased their land holding to about 1,650 acres. The Hawke's Bay Almanack and Directory for 1894 reported that William Siteman of Spring Hill, Wimbledon, owned 1,400 sheep. By 1898 they were able to employ a manager for the property, Charles Burtton. Isabella Siteman took part in the social life of the local community and was reported as being 'an acquisition as a singer and a popular figure at country concerts'.
On 28 September 1917 William Siteman died, aged 83 years. Isabella Siteman's health was poor, so she sold the farm and left the district. She died in Dannevirke on 18 March 1919. There were no surviving children of either of her marriages.
Although lacking formal education, Isabella Siteman was aware of the benefits it could confer. She decided to devote a large part of her savings to the better education of students who required financial help. Her will left the residue of her estate in trust for this purpose. The Isabella Siteman Scholarship was founded in 1923 and was intended to provide assistance to young men and women who wished to obtain a university education in New Zealand. Initially one scholarship was offered every two years, carrying an award of £80; later one scholarship was offered each year. Under the original terms of the scholarship the holder was required to take a science degree at the University of Otago. Numerous changes were made to the criteria, and eventually the scholarship was made open to all prospective university students from the Hawke's Bay area.
Isabella Siteman had few advantages in life. After much hardship and sacrifice she found herself with the means to assist others in improving their lot. The Latin inscription on her headstone in the Mangatera cemetery, Dannevirke, reads: 'Ipsa non educta vos in scientia duco' (Although not educated myself, I lead you into knowledge).