Nellie was a nurse at Royal Prince Alfred Hospital in Sydney, and forged the way for training and education of civilian nurses for military service during the Boer War and in World War I.

By far her most meritorious contribution began when she was asked in February 1899 to help form the Army Nursing Service and become one of Australia's first Boer War nurses. In May of the same year the first 26 official military nurses were sworn in, handpicked by Nellie herself. Nellie had chosen her nurses only from those who had had more than seven years of nursing experience.

When war broke out again in 1911, Nellie’s experience as an Army nurse in the Boer War gave her the invaluable knowledge and understanding to lead Australia’s first contingent of nurses bound for Europe in World War 1. In September 1915, Nellie and 96 Australian nurses prepared for the influx of casualties which followed the first landing in Gallipoli.

At the end of her career, Nellie’s uniform was weighed down with medals, and in 1916 she was awarded the Royal Red Cross (1st class), a medal which is conferred upon members of the nursing services, irrespective of rank, who are 'recommended for special devotion and competency in their nursing duties'.