Dr Bell was brought up in Canada, and studied at Harvard University graduating summa cum laude in History and Science at the age of 20. She was a Commonwealth Scholar at the University of Oxford where she studied for her doctorate in the history of medicine under the supervision of Professor Megan Vaughan, FBA. She was a member of Nuffield College. She was a Rhodes Research Fellow at St Hilda's College, Oxford during which she published academic articles, taught undergraduates and converted her D.Phil. thesis into "Frontiers of Medicine in the Anglo-Egyptian Sudan, 1899-1940." 
Before taking up her post at Oxford she worked at McKinsey & Company in their Toronto and London offices, becoming a partner. At McKinsey she provided advice to international companies, research councils, charities and the public sector and led sizeable teams working on various projects.