After graduating she worked in a local dispensary before moving to Edinburgh, her mother's birthplace, where she worked as assistant to Elsie Inglis, at the Edinburgh Hospital for Women and Children at Bruntsfield. The hospital had been established by the pioneer of medical education for women, Sophia Jex-Blake. Following this she worked in a mission hospital in Gaza, where she gained valuable surgical experience. At the outbreak of World War I her application to serve as a field surgeon was accepted by the War Office, but the chief medical officer of the unit she was to join refused to accept a woman surgeon. She applied to Elsie Inglis, who had founded the Scottish Women's Hospitals organisation, and Inglis happily accepted her former assistant as a surgeon in the SWH hospital unit at Royaumont near Paris, the first SWH unit to be set up. She became second-in-command of the unit under the chief medical officer Frances Ivens, with whom she shared the bulk of the major surgical workload. In May 1918 the bed complement at Royaumont was, at the request of the local French commanders increased to 600 beds. As a result, in July 1918 there were so many admissions that three theatres worked all day and two worked all night. Vera Collum wrote "I do not think the médecin-chef Frances Ivens or the second-in -command Miss Nicholson ever got more than three hours rest in the 24 during that strenuous fortnight." For her service in treating French soldiers at Royaumont, she was awarded the Croix de Guerre and the Médaille d’Honneur des Épidémies by the French government.
Post war career
Inspired by her chief Frances Ivens, she decided on a career in obstetrics and gynaecology. Working as a general practitioner in Birkenhead, she prepared for the necessary examinations and became a founder member of the Royal College of Obstetricians and Gynaecologists in 1929. Following a recommendation from Frances Ivens she was promoted to Fellow of the College in 1931. She was appointed Clinical Lecturer and Gynaecological Surgeon at the University of Liverpool in 1930 in succession to Frances Ivens and held consultant appointments at Liverpool hospitals in addition to her own private practice. She was the first woman president of the North of England Society of Obstetrics and Gynaecology.
Later life
She retired to South Devon. Like many of her former colleagues at Royaumont she continued to attend Royaumont reunions until 1960. Towards the end of her life she was nursed by a former Royaumont sister. She died in Exeter in 1963 at the age of 77.
