Her parents were Georga ("Goggi") Wilhelma Ellertsen (1871-1959) and politician Adam Egede-Nissen (1868-1953). Her siblings Aud Egede-Nissen, Ada Kramm, Stig Egede-Nissen, Lill Egede-Nissen and Gøril Havrevold became actors as well. Gerd made her acting début at the Nationaltheatret in 1910.
During the German occupation of Norway Gerd and Nordahl Grieg were active in supporting the Norwegian war effort from exile.
Gerd Grieg mostly stayed in the United States and the United Kingdom, "entertaining Norwegian seamen like a Norwegian Vera Lynn". Nordahl Grieg died in 1943.
Gerd retired in 1955.