Though Warren was drawn to surgery as a student, she was trained in obstetrics, as females were unable to study surgery formally at the time of her medical education in the 1950s. On completion of her three hospital positions, St George, Queen Victoria in Melbourne and Geelong, providing good experience, hands on, in a wide range of medical areas, she completed her Diploma of Tropical Medicine and then took up a position in Korea as locum tenens at a women's hospital run by the Australian Presbyterian Mission. During her 18 months in Korea she developed a passionate interest in the treatment of sufferers of leprosy. Subsequently, her next locum position was at the Leprosy Hospital in Hong Kong, on the island of Hay Ling Chau. When she commenced there in 1959, the facility lacked a surgeon to staff their newly established reconstructive surgery unit, and so Dr Warren herself was trained in basic surgical procedures by a fellow physician. She was keen to master these skills and so augmented this training by reading all she could in text books. In the same year she hypothesized and then proved that by applying a plaster cast to a neuropathic foot for a prolonged period of time it was possible to heal fractures previously considered treatable only through amputation. Her skills in surgery also soon became apparent, and she rapidly became sought out to instruct doctors and surgeons in surrounding countries.

In 1962 she became a permanent staff member at the Hay Ling Chau Leprosy Hospital where she continued to successfully treat countless cases, all the while documenting her research and development of treatments. In 1972 she submitted this research work to the University of Sydney and was awarded a Master of Surgery. The Hay Ling Chau Leprosy Hospital was closed in 1975, but she continued to teach throughout Asia on behalf of the Leprosy Mission International until early in the 21st centaury. From 1964 this was fulfilled by constant traveling in order to teach all levels of local medical staff to be able to utilise the materials that they had available, to meet the needs of their patients. This proved much more satisfactory in spreading the modern methods of rehabilitation, than the old routine of send the senior medical officer, of the center, to one of the main Leprosy Teaching centers as all staff benefited and we could help them to adapt what they had available to minimise the needs to import materials etc. Hence reduce the financial costs needed to upgrade the leprosy service.

In 1989 she was officially retired from full time overseas service with the Leprosy Mission International, but because of repeat requests to go and help she continued to work overseas for many months each year until 2012, working in a total of 26 countries. In this period of time she acted as consultant and teacher for leprosy clinics in several states of Australia. From 1989 she found that during the intervals when she was in Australia she could share her experiences relevant to any other people with neuropathy, especially diabetic patients and others with foot problems due to loss of sensation or muscle power, eg CMT. This was a period when diabetes was becoming more common and the effects of the neuropathy were just being appreciated.

While still teaching throughout Asia, in order to spread the knowledge of the effective treatment she had pioneered she also took part in seminars, when in Australia, for Australian doctors and surgeons. This work culminated in the publication, with the co-operation of Professor Sydney Nade of The Care of Neuropathic limbs- a Practical Manual in 1999. Dr Warren continued to assist, consult and teach in surgery and Leprosy, in Asia and Australia, into her mid eighties.