She earned a Bachelor of Fine Arts from the University of Texas at Austin in 1975[2][3] and later made her Broadway debut in the musical Rex.

[1] Mahaffey was a regular cast member in the soap opera The Doctors from 1979 to 1981, which earned her a nomination for Daytime Emmy Award for Outstanding Supporting Actress in a Drama Series in 1980.

[citation needed] Mahaffey played Alma Hodge in season 3 of ABC comedy-drama series Desperate Housewives from 2006 to 2007.

Mahaffey made guest appearances on Quantum Leap, L.A. Law, Ally McBeal, Judging Amy, The West Wing, Law & Order: Special Victims Unit, Frasier, CSI: Crime Scene Investigation, Private Practice, Boston Legal, Without a Trace, and Raising Hope.

[9] In 2016, Mahaffey played a supporting role as Diane Higgins in the biographical drama film Sully directed by Clint Eastwood.

[10][11] In 2020, Mahaffey starred opposite Michelle Pfeiffer in the comedy-drama film French Exit playing widow Madame Reynaud.