O'Regan was born in Montreal,[1] in 1891, the daughter of Cordélia Désy and Pierre Gauthier.
[5] O'Regan ran for a seat in the Canadian House of Commons in a by-election in 1936 in the riding of Ottawa East as an Independent Liberal.
[13] O'Regan decided to run for the seat after losing the Liberal nomination to Pinard.
[14] In the nomination meeting, O'Regan won 1,100 votes to Pinard's 2,149 on the first ballot, finishing third, and was eliminated.
[19] Also in 1950, O'Regan spoke on behalf of the candidacy of Charlotte Whitton, who was running for a spot on Ottawa's Board of Control in the 1950 municipal election.
[23] On March 28, 1960, O'Regan was elected by city council to fill the vacancy in St. George's Ward following the resignation of May Nickson who was moving to Canberra, Australia.
At the time of her election, she was president of the District 10 Ontario Hospital Ladies' Auxiliary,[25] and the Alumni Association of Notre Dame Convent.
[8] O'Regan ran for re-election in the 1962 municipal election, running on a platform of more hospitals and a home for the aged.
[32] On election day, she lost her seat, finishing just 188 votes behind second place David Dehler.
She defeated former alderman Clem Aubin among a vote of council members to fill the By Ward seat, which had been vacated by Jules Morin, who had been appointed to the city's Board of Control.
[39] She later revealed one of the reasons for her push was after hearing of a three-year old who starved to death in the city, but that she would be arrested if she had done anything about it.
[47] In early November 1966, O'Regan announced her intention to run for re-election in the 1966 municipal elections.
[48] On election day, she went down to defeat, with Rhéal Robert finishing second in the ward, over 800 votes ahead of the 1,919 that O'Regan won.
[49] In 1968, when Wellington Ward became vacant following the death of Lionel O'Connor, O'Regan was one of the candidates considered by council to replace him.