Daughter of a nurse and an Irish army officer, Sonja had a somewhat disrupted childhood, anchored by some happy years with her maternal grandparents. She left school at fourteen and worked in a variety of jobs before trying some university study, undertaking training as a nurse, having a brief marriage, and a daughter born to an American serviceman who was killed in action. After a long battle with tuberculosis, Sonja married again and settled in Nelson. Here she became active in local body work, and spent nine satisfying years on the city council and hospital board, helping to meet people’s needs. She was also involved in the union movement, and promoted the rights of workers, especially women, in wider national positions and in international forums. In 1978 she became the first woman executive member of the Federation of Labour, and its vice-president in 1983. A founding member of the Working Women’s Council, she served on many committees and councils, developing strategies for recognising and valuing women’s work, both paid and unpaid, for instance initiating the New Zealand Childcare Association and chairing it for many years.

In 1987 Sonja Davies entered parliament and for six demanding years served on select committees related to foreign affairs, defence, and disarmament. She was widely respected and honoured for her dedicated and determined work, in the face of personal setbacks and tragedies, to foster the well-being of women, children, and the underprivileged.