During the Japanese Occupation, she worked as a canteen operator with her husband at the Mental Hospital which was renamed 'Miyako Hospital' (the predecessor of Woodbridge Hospital) where patients from General Hospital had been moved to. It was an activity for which they were to pay dearly after both were arrested by the Japanese. They secretly brought food, medicine, money, messages and even radios to British internees. She and her husband, Choy Khun Heng, incurred further risk by sending in radio parts for hidden receivers on a daily ambulance run until the Japanese instituted a crackdown after a British-Australian commando raid sank seven Japanese ships outside the harbour in September 1943.

'The Kempeitai', the Japanese military police, suspected that the raiders had acted on information sent out from Changi by a transmitter, and seized 57 internees on October 10 1943, setting in motion what became known as "The Massacre of the Double Tenth". Believing their activities were related to the Double Tenth incident, they came under surveillance by the 'Kempeitai', the Japanese military police. Unfortunately, they were caught by the Japanese and Elizabeth was arrested on 15 November 1943 and taken to a cell in the old YMCA building in Orchard Road, following her husband's arrest and confined to the Outram Prison on 29 October 1943.

Her psychological resilience and principled stand sustained her endurance in the physical abuse and interrogation at the hands of the 'Kempetai' and she never admitted to being a British sympathizer. This exploit had been carried out by a group of Australian and British commandos, and the Japanese were convinced that British prisoners in Changi Jail, somehow helped by the Choys and others, had supplied information useful to the attackers. She was released only after 193 days of starvation diet and repeated torture. She spent 193 days in a stinking cell 10ft by 12, occupied by more than 20 people, of whom she was the only woman. To add to the psychological pressure on her husband, she was frequently taken out and tortured in front of him, stripped naked while electrodes were inserted into her body. Her husband was released when the Japanese Occupation was over.