Born in Petrolia, Ontario, Stephenson began her career at Bell Canada in 1973, after graduating from the University of Toronto with a Bachelor of Arts degree.
She rose to become an executive in the corporation in 1988 and held various senior positions at the company, including Vice President of Bell Canada and President and Chief Operating Officer (Americas) of BCE Media.
In 2001, she received the Woman of Distinction designation from the YWCA, and in 2005, Stephenson was inducted into the Hall of Fame of the Canadian Information Productivity Awards for her contribution in building a competitive telecommunications industry in Canada.
From 2015 to 2019, she was chair of the Board of Directors for the Trillium Network for Advanced Manufacturing, in London, Ontario.
[1] Along with her Bachelor of Arts degree, Stephenson completed the Executive Program at the Graduate School of Business Administration, University of California at Berkeley in 1989, and the six-week Advanced Management Program at Harvard Business School in 1994.