At their Lithgow home, Cook studied in the evenings, moving from writing and grammar to typing and shorthand, and then to book-keeping.

[2] By 1891, six years after their marriage and emigration to Australia, the couple had three small sons, and Joseph Cook had a seat in the New South Wales parliament.

She spoke at meetings there in the 1919 election campaign, and also deputised at ministerial events, such as the unveiling of an Honour Roll dedicated to the 1914–18 servicemen and women in General Granville Ryrie's Manly electorate.

[citation needed] During her husband's term as High Commissioner, Mary Cook played a key role for the Australian Red Cross Society, including representing the Society at a meeting of the International Red Cross Board of Governors in Paris in 1923.

[4] Mary Cook's services to Australia were acknowledged when she was created a Dame Commander of the Order of the British Empire (DBE) in 1925 Birthday Honours List.