Buller was born in Crediton, Devon, the only daughter of General Sir Redvers Buller and his wife, Lady Audrey, youngest daughter of the 4th Marquess Townshend. 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. She was also responsible for forty-four affiliated auxiliary hospitals. By 1918 more than 35,000 patients had passed through the hospital. For her work she was appointed Dame Commander of the Order of the British Empire (DBE) in the 1920 civilian war honours and also awarded the Royal Red Cross 1st Class (RRC).
After the war, Buller began collecting funds to establish an orthopaedic hospital for children in Devon. In 1927 she opened the Princess Elizabeth Orthopaedic Hospital in Exeter. In 1937 this was followed by the St Loye's Training Centre for Cripples (later St Loye's College for Training the Disabled) in Exeter and Queen Elizabeth College in Leatherhead, Surrey. She also founded the British Council for Rehabilitation.
Buller died at her home in Exeter from cancer in 1953.