Johnsen worked for the Norwegian shipping company Wilh. Wilhelmsen as a messroom girl. She worked on board MV "Tudor", which was in the Mediterranean Sea when Germany invaded Norway on 9 April 1940. The ship left Gibraltar on 12 June and sailed in convoy for United Kingdom. On 19 June 1940 MV "Tudor" was torpedoed and sunk northwest of Cape Finisterre by the German submarine . Johnsen and the rest of the crew, except one, survived the sinking.