Ruth Gunderson was the daughter of Federico Demée Baretto and Olive Jones. She was British by birth but presumably became Norwegian when she married a master mariner called Olav Gunderson at St. Andrew's, Kowloon.
This was a second marriage: on January 17, 1935 she'd married Filomeno M. G. Ozorio, the first (and youngest) Portuguese to sit on the Sanitary Board. He died on February 13, 1937. (http://hongkongsfirst.blogspot.co.uk/2013/07/biographical-dictionary-of…)
Her husband contracted malaria in 1941 so the family, which included a daughter Désirée, were ashore in Hong Kong when the Japanese attacked. Désirée was a child of her first marriage and she had two other daughters and one son who were presumably not with her during the occupation (Hongkong Daily Press, February 15, 1937, page 1)
The Norwegians were allowed to stay uninterned in 1942, but on a 'one for all' parole, which was considered breached when two nationals escaped in February 1943, with the result that the rest of the community were interned.
It's not clear why Ruth Gunderson was allowed to remain in town: she herself tells us that the only people exempt were the over 60s and missionaries. She doesn't seem to have been a missionary as she makes no mention of her dealings with Chinese Christians. Moreover, one of the escapers, Captain Kvamso, was living in the same house as her when he left Hong Kong, and the Japanese were angry and suspicious and put a watch on the premises.
Her reason for staying out of Stanley was to send her husband food parcels and to press the Japanese to allow him to leave camp to get treatment for a back injury.
Her daughter eventually escaped by junk to Macao, but she remained in town until the end of war, later writing an invaluable short account of the occupation.
Source:
HK PRO, HKMS100-1-6