Hired to work as a typist for the Irish Folklore Commission, she remained there until its disbanding in 1970, simultaneously developing a second career as a journalist, serving as a theatre critic and writing the women's page for The Sunday Press.

[2] Through her work at the Commission and the paper, she befriended J. R. R. Tolkien on some of his trips to Dublin, famously introducing him to fish and chips soaked in vinegar.

On a trip to California in 1968, she met and talked with Robert F. Kennedy in Los Angeles airport as he arrived to address his supporters and she was en route back to Ireland.

[9] Mahon was appointed to serve as the negotiator on behalf of the Commission's staff with the Department of Education and Finance to resolve their grievances on pay and pensions.

[16][17] The book provided insight into how rich and varied the diet of common people was in the 17th century before industrialisation and land reforms brought about the Great Famine.

In 1959, Darby O'Gill and the Little People premiered in Dublin and members of the commission who had helped gather information for the film, including Mahon, were given tickets to attend.

[2] Mahon died at Leopardstown Park Hospital in Dublin on 20 February 2008 and was buried the following day at Mount Jerome Cemetery and Crematorium.