Rosalie Davies was born on January 22, 1939, in London, England. She grew up in England and married her husband, with whom she moved to Montreal, then New York, and then Philadelphia in the 1960s. She became involved with lesbian life through her job at an insurance agency and the bar scene, and then left her husband, with whom she had three children, in 1968. In the late 1960s she attended the University of Pennsylvania, where she earned a B.A. in English and Philosophy, and became involved in the women's movement, the Homophile Action League, and Radicalesbians.

In 1973, Davies sued for custody of her children, which was denied due to her sexuality. This prompted her to start Custody Action for Lesbian Mothers, an organization to educate lesbians about custody issues and provide pro bono legal support for women facing discrimination in custody cases based on their sexuality. She attended law school at Temple University to become a lawyer and work on these cases herself, graduating in 1979 and later becoming a member of the National Lawyers Guild, the Montgomery County Bar Association, and the Pennsylvania Bar Association. She also belonged to the National Community Relations Committee of the American Friends Service Committee (1978-1988) and the Eromin Center Board of Directors (1976-79). She died on July 14, 2009. Davies discusses her life and her activism in her interview with the Philadelphia LGBT History Project, 1940-1980, by Marc Stein.