She attended the Beresford Street Public School before becoming one of the first girls to attend Auckland Grammar School in Symonds Street.
Edith married Joseph Henry Blackwell in 1932. Following a time in Kaiapoi they returned to Auckland building Marewa a fine home on the north-eastern slopes of Mount Eden with fascinating gardens spreading down the hillside.
In 1950 Edith established a charitable trust the Edith Winstone Blackwell Foundation - which was incorporated in 1956. A Trust Board appointed to run the trust included a representative of the descendants of each of Edith's brothers. Edith donated a Zeiss telescope to the Stardome Observatory. The primary fixed telescope at Stardome Observatory is named after her.
In 1954 Edith was awarded an MBE by Her Majesty the Queen; the award was presented at Government House in Auckland on 25 February 1955 by the Governor General Sir Willoughby Norrie. She died on 15 September 1956.
The Edith Winstone Blackwell Case Room in the Owen G Glenn Building at the University of Auckland is named after her.
In 2008, the University of Auckland launched a fundraising campaign to redevelop the Leigh Marine Laboratory at Goat Island, Auckland as the base for the South Pacific Centre for Marine Science - with a $4.5 million donation from the Edith Winstone Blackwell Foundation.