By 1891, McCarthy was in England, and on 10 October 1891, entered The
London Hospital,
Whitechapel, to begin general nursing training as a probationer. She trained under
Eva Luckes between 1891 and 1893. Hospital records state that "she had an exceptionally nice disposition" and was "most ladylike and interested in her work" although "she found it hard to control others, or to take firm action when necessary". She was nonetheless promoted to sister in January 1894. McCarthy was Nursing Sister-in-Charge of the Sophia Women's Ward at the outbreak of the
Second Boer War, and was one of the six sisters selected from The London Hospital by Princess Alexandra to go to South Africa as her own "military" nursing sisters. Resigning from the hospital on 25 December 1899, McCarthy served with distinction throughout 1899–1902 with the Army Nursing Service Reserve, receiving the Queen's and the King's Medal and the
Royal Red Cross. Returning to England in July 1902, she was awarded a special decoration by
Queen Alexandra. She then became involved in the formation of
Queen Alexandra's Imperial Military Nursing Service, was promoted matron within the service in February 1903 and during the next seven years was successively matron of the
Cambridge Military Hospital at
Aldershot,
Netley Hospital and the
Queen Alexandra Military Hospital in
Millbank. In 1910 she was appointed principal matron at the War Office, a position she held until the outbreak of the
First World War. She was matron-in-chief of the
Territorial Army Nursing Service from 1920 until her retirement in 1925. She became a member of the
Royal College of Nursing in 1920. ==Personal life==