In 1940, at the age of 32, Jeffrey volunteered for the Australian Army Nursing Service, Australian Imperial Force. She embarked for Malaya where she joined the 2/10th Australian General Hospital in Malacca. The 2/10th was moved to Singapore on the 18th February 1941.She was evacuated from Singapore on February 12th 1942 aboard a small coastal steamer, the Vyner Brooke. The steamer was attacked and sunk by Japanese bombers in the Banka Strait on 14th February 1942.Jeffrey and another nurse, Iole Harper spent three days in the water, resting in mangrove swamps and up trees until they found a native village. The nurses were persuaded to give themselves up to the Japanese. They rejoined the other Sisters who had made it to shore.The 32 Sisters who survived the shipwreck in the Banka Straight, spent the next three and a half years as prisoners of war on Banka Island and Sumatra. Of the original 65 nurses evacuated from Singapore on the Vyner Brooke, only 24 returned to Australia. During their internment, eight Sisters died in the last seven months before freedom, due to malnutrition and other easily treated diseases.During her time in the camp Jeffrey stole two exercise books from the Japanese. In these books she wrote a diary of their life in camp. Jeffrey also kept many scraps of paper and another note book full of drawings of life in camp, recipes and music written for her performances as part of the Womens' Choir. Imaginary dinners were held where they would describe the lovely food they imagined having. Jeffrey's drawings depict many of the individuals and scenes that are part of White Coolies.During her imprisonment, Jeffrey became very ill with malaria, beri beri, recurring appendicitis, Banka Fever and tuberculosis. Jeffrey weighed 30 kilograms at the end of the war. On her return to Australia she spent a further two years in hospital. She never fully recovered her health.In 1947, after leaving hospital, Jeffrey and Bullwinkel drove throughout Victoria visiting hospitals, telling of their ordeal and collecting donations to build a "living memorial" to the nurses that never came back. The Nurses Memorial Centre still exists in St Kilda Rd Melbourne. Jeffrey was appointed the first administrator of the Memorial Centre.In 1950 Jeffrey and Bullwinkel travelled to the United Kingdom. They were presented to King George VI, Queen Elizabeth and the Queen Mother.Jeffrey's book White Coolies became a best seller and was serialised in The Sunnewspaper in 1954 and on the radio. Movies such as Paradise Road and Women in Captivity have usedWhite Coolies for inspiration. The 19th edition of White Coolies was published in 2000.After burgeoning poor health Jeffrey was forced to retire from the Nurses Memorial Centre. In the 1960's she acted as a golf caddy to her friend, Burrta Cheney, the Victorian champion golfer. Betty spent much of her time doing volunteer work for the Ex-Prisoner of War and Nurses Memorial committees.During the last decades of her life Jeffrey spent much of her time answering correspondence in relation to her book. She was often invited to be a guest speaker relating her prisoner of war memoirs.Jeffrey was awarded the Medal of the Order of Australia in 1987 for her services to ex-servicemen and women. Betty died in September 2000 at the age of 92.