With the Liberal Party, she ran for a seat in the Senate at the 1961 federal election; she defeated Frank McManus and took office in July 1962.

Breen died in 1993; she was memorialised by senator Rod Kemp as a "remarkable woman with great strength of character".

[3] Her father, Frederick William Chamberlin,[2] was born in England; as a teenager, he immigrated from Devon to Australia and found employment as a town clerk in St Kilda.

The pair married in St Kilda on 12 December 1928 and had three daughters together;[2][3] two of them, Prudence Griffiths and Jeannette Patrick, would also later become involved in politics at various levels.

[4] She initially had little interest in seeking election to the Senate, as she did not want to be separated from her family for long durations of time.

[2] Among other causes, she advocated for the abolition of Australia's marriage bar, financial support for widowed and deserted wives, and the inclusion of women in official positions.

[2] She was an admirer of the first female Australian senator, Dorothy Tangney, due to her work on behalf of the people of Western Australia.

She involved herself in the Colombo Plan, an international organisation providing humanitarian and financial aid to developing countries, especially in Southeast Asia.

[4] While preparing for the Select Committee on the Metric System of Weights and Measures' first convention, Breen learned that her husband had been involved in a major car crash.

Following this crash, she resigned from the committee[2][3] and became largely inactive in the political field, devoting much of her time towards caring for Robert.

[2] She chose not to seek reelection in the Senate in order to continue caring for him, and retired at the end of her term on 30 June 1968.

[8] Breen was appointed Officer of the Order of the British Empire in 1958 due to her work as the Victorian president of the National Council of Women from 1954 to 1958.

She was memorialised in the Parliament of Australia by senator Rod Kemp two months after her death, who called her a "remarkable woman with great strength of character".