Prieur was a controller in the intelligence-gathering and evaluation wing of the DGSE, acting as Christine Cabon's controller. She was a specialist in European peace movements. Prieur entered New Zealand on a Swiss passport issued to her alias of "Sophie Turenge", posing as the wife of Alain Mafart. She took part in the operation that bombed and sank the Rainbow Warrior, killing the photographer Fernando Pereira.
After her arrest by New Zealand police, along with her colleague Mafart, she pleaded guilty to charges of the manslaughter of Pereira and was sentenced to 10 years imprisonment on 22 November 1985. After serious political pressure from France and her allies, the New Zealand government agreed to a United Nations arbitration ruling in July 1986 that saw her transferred to French custody on the island of Hao in French Polynesia.
On 6 May 1988 she was returned to France because she was pregnant (her husband was allowed to join her on Hao). Like Mafart, she never returned to Hao. She has since been promoted to the rank of Commandant. Although a UN Arbitration panel found that France had breached its obligation to New Zealand several times by removing the agents from Hao, and failing to return them, it rejected an appeal by New Zealand to have Mafart and Prieur returned because the term they should have spent there had already lapsed.
Prieur published a book "Agent secrète" (Secret Agent) concerning her role in the bombing.
- BBC NEWS | World | Asia-Pacific | French expat recalls NZ bombing
- "At the end of the Rainbow - National - NZ Herald News". Nzherald.co.nz. Retrieved 2014-01-13.
- Staff (4 January 2009) "Fresh Start for Saboteur" Sunday Mail (South Australia) p. 29