The daughter of Thomas Easterfield and Anna Maria Kunigunda Büchel, she was born in Wellington, New Zealand, on 26 February 1900.
[1][2] Her father was a founding professor of chemistry at Victoria University of Wellington and director of the Cawthron Institute in Nelson from 1919 to 1930.
[2][4] After the death of her husband and a short period working at Wellington Hospital Deem went to England in 1934 to study paediatrics, gaining the Diploma of the Royal College of Obstetricians and Gynaecologist in 1935.
[2] Returning to New Zealand in 1936 she joined the Health Department as a school medical officer in the South Auckland District and assistant to Dr Harold Turbott.
[2][4] With the Plunket Nursing Advisor, Nora Fitzgibbon, Deem carried out the first height and weight survey of nearly 9000 New Zealand infants.
[4] In the 1952 New Year Honours, Deem was appointed an Officer of the Order of the British Empire, for services as medical advisor to the Plunket Society.