[1] Born in Dundee, Fenwick was educated at Stobswell School, leaving at the age of fourteen to undertake an apprenticeship as a weaver at the Scottish Co-operative Wholesale Society's Taybank Works.
She followed in a family tradition of becoming an active trade unionist, joining the Dundee and District Union of Jute and Flax Workers, and within a year achieved success in campaigning for apprentices to be paid at the same rate regardless of age.
[2] She tried to become a shop steward in 1950, but the company management refused to allow this, claiming that because she was married and had young children, she would be unable to fulfil the role to the same standard as a single person.
She was elected as Assistant General Secretary in 1960,[4] then as General Secretary in 1971. she served on various government committees relating to the jute industry, and was made a Member of the Order of the British Empire in 1973.
[2] In 1976, Fenwick served as chair of the General Federation of Trade Unions, the first woman to hold the post.