She acted as the chief for advertising campaigns on behalf of Bill Blass, Elizabeth Arden, and Blackglama mink, among others.
Her first advertising job was for the Chicago department store, Carson, Pirie, Scott & Co. as copywriter after a period in the retail shop as receptionist.
[1][2] For the lingerie and hosiery company, Julius Kayser Inc., she created an in-house agency, Advertising Associates, after she moved to New York in 1956.
Between 1965 and 1966 the agency worked for well known companies including Charles of the Ritz, Rob Roy Shirts for Boys, Pauline Trigere, Elizabeth Arden, and Union Carbide Corporation's textile department.
[1][2] During her career, her agency created advertising campaigns for clients including Bill Blass, Elizabeth Arden, and Olivetti.
[1][2][4] For her campaign for the Great Lakes Mink Association, her employee Norman Sunshine created the slogan "What Become a Legend Most?"
and employee Peter Rogers persuaded major stars like Lauren Bacall, Marlene Dietrich, Bette Davis, and Judy Garland to pose in a Blackglama mink coat under the slogan, "What becomes a legend most?"
[1] Trahey attempted to get credit for creating many of the slogans that her employees came up with, as detailed in Norman Sunshine's 2011 book Double Life.
Her novel Life With Mother Superior was the basis for the film The Trouble with Angels, starring Hayley Mills and Rosalind Russell.