Born in Jamaica, Williams studied at Oxford and trained at King's College Hospital after wartime delays. Limited posts for women contributed to her entry into the Colonial Medical Service, which offered responsibility while governing colonised populations through racial hierarchy.
Transferred from the Gold Coast to Malaya, she developed maternal-child services. During the Second World War she was imprisoned by Japanese forces at Changi, where hunger and disease made nutritional knowledge urgently practical.
In 1948 she became the first head of maternal and child health at the World Health Organization. Later teaching and advisory work carried her across several regions but also raised the recurring question of how international experts should value local workers and knowledge.