Ratahi was a tamaiti whangai of Arthur and Iwingaro Stewart in Gisborne, New Zealand. As a young woman she moved to Wellington, where she helped found the Maori Women's Welfare League, and advised the Department of Maori Affairs and Te Puni Kokiri. She worked with young people in trouble and helped start the kohanga reo movement for Maori-language pre-school education.
She and her husband, Lionel Ratahi, had a born-to son and a tamaiti whangai.
She received the Queen's Service Medal and the Order of New Zealand.