Maude was born into a family of school teachers, her mother, father and aunt were teachers and Maude and her sisters, Mabel and Gertrude became teachers. Mabel was born in Holborn on 15th May 1942 and baptised at St George, Hanover Square, London, Westminster, on 17th June 1942. Maude was the first child of Charles Emilius Johnstone, 36, and Eliza Johnstone, nee Hitchcock, 31. Her sister Mabel was born the following year and her sister Gertrude was born 3 years later. Her brothers Charles and Edward were born in 1849 and 1853 respectively.
By 1851, Maude and her sister Mabel were living with their aunt, Anne Bigg, a governess, in Clifton, Bristol while their cousin Alfred was living with her parents in Beaconsfield as a pupil at their school. Her father died in 1860 in Woodspeen, Newbury, Berkshire and the family moved to Worthing in Sussex.
Her mother, Eliza, was a working widow and set up a school for young ladies in 1860 at Marlborough House, Marine Parade, Worthing. It was a family affair with cousins joining them at the school, Maude was a qualified teacher and Mabel and Gertrude became teachers at Marlborough on Marine Parade where their pupils boarded. Their landlord was widower, John Forbes Hardy, a landscape painter and property owner. He lived next door to them at Marlborough Terrace where their brother Edward lodged.
John courted Maude and they married on 12th February 1877 at Christ Church Worthing. They bought a house on Manor Road Worthing and named it Beaconsfield after the town where their parents were teachers when Maude was little. They had a housemaid and a cook and Maude's maternal aunt Julia came to visit. By 1891 her sister Gertrude who had retired from teaching, moved in with her sister and brother-in-law. In 1892, Eliza, Maude's mother died.
Maude's husband, John, died in 1906 and he was buried in a grand plot at Heene Cemetery. Maude sold her home after inheriting John's estate and bought a nearby house on Wordsworth Road, Worthing. She named it Woodspeen after the place where her father died near Newbury. Her sisters; Mabel and Gertrude joined her and they lived together for their final years at Woodspeen.
Maude died on 16th December 1920 at Woodspeen, Wordsworth Road, Worthing. She was buried at Heene Cemetery on 20th December 1920. She left her estate of £10903 4s 11d to her sisters; Gertrude and Mabel and her nephew, Reverend Rupert Johnstone, a clerk in holy orders.