 She joined the British Red Cross Society and by the outbreak of the First World War in 1914 she was Deputy County Director of the Voluntary Aid Organisation for Devon.She was asked to establish a hospital in Exeter; by August 1915 the original 160 beds had grown to over 1,400.Established as the Red Cross Voluntary Aided Hospital, in 1915 it was taken over by the War Office as the Central Military Hospital Exeter and Buller remained as administrator, the only woman to hold such a post in a major military hospital during the war.