In June 1940 Whitworth joined the
Women's Australian National Service where she participated in outdoor exercises and undertook courses in map-reading, signalling and military administration. She was soon promoted to honorary lieutenant and, by June 1941, honorary captain and commandant of the Eastern Suburbs defence unit which was made up of over 100 women. In August 1941 Whitworth volunteered for the newly formed
Australian Women's Army Service following her recommendation by
Margaret Loder Wakehurst who called her a 'born leader' and 'very steady and dependable'. There she was made a captain in January of 1942 and soon after she was appointed chief instructor of an AWAS recruit training school in
Killara. In July 1942 Whitworth was promoted to temporary major, a role that would become permanent in 1944, and from September 1942 took over the 2nd AWAS Training Battalion where she gained the nickname 'Bertha Blitz'. For the remainder of the war she worked in various positions in one of which she met and formed a close friendship with Barbara Gilchrist Donkin, a captain within the Australian Army Medical Women's Service and they became lifelong companions. == Post World War II ==