Elizabeth, then known as Nellie, was the granddaughter of a Scottish missionary who had administered to the poorest of the poor in South India for fifty years http://www.britishempire.co.uk/article/faithandfamily.htm . Her home was therefore in the Palani Hills of South India where she was born. Educated at Ancaster House, Bexhill-on-Sea in England, she then started working in November 1914 as an unpaid volunteer at the Red Cross hospital in Bexhill. On 7 May 1916 she was sent to France, initially to Boulogne, as an orderly and driver. She remained in France for three years being released by the Red Cross on 1 May 1919. On the 8 July 1919 her ‘Mention in Despatches’ was promulgated. Copies of her letters home from France are held by the Imperial War Museum.
Nellie’s elder brother, Maunsell Mayne, a professional soldier who was commissioned into the Royal Artillery from RMA Woolwich in September 1914, was fighting in France & Belgium (1914-15 Star) and Italy (MC 1918, Italian bronze medal for valour). Maunsell survived the war but suffered from its after-effects and disappeared in 1927, later presumed dead. He left a son, Peter Maunsell Mayne (born 1922), whose whereabouts are unknown.
You can read more at https://www.scribd.com/doc/75988391/Sedborough-Mayne-of-Ireland pages 36-38.