[5] In 1976, Hennessee started her business career at Thomson McKinnon Securities, where she executed institutional and retail sales.
She started the Hennessee Hedge Fund Advisory Group in 1987 as a division of E.F. Hutton, later moving it to Shearson Lehman, Republic National Bank, and the investment firm Weiss, Peck and Greer.
[8][9] Hennessee was a featured hedge fund expert in the media such as The New York Times, The Wall Street Journal, and CNBC.
[14] Hennessee was a trustee of Palm Beach Atlantic University and national chairwoman and founding member of Easter Seals Florida's annual Kentucky Derby charity event.
She served as a finance chair for Elizabeth Dole's presidential campaign and the 2005 New York City Billy Graham Crusade.
In addition, Hennessee co-founded the New York City Christian Women's Fellowship, which folded into Campus Crusade.