After discovering a love for history in Texas, Bonnel went to the Université de Genève, Switzerland, while her husband was serving at the headquarters of the World Health Organization from 1951.
Upon completing her doctorate, Bonnel immediately began to work in the field of naval history and quickly became a key figure in reviving this subject that had long been neglected by universities in France.
In 1964, she was appointed the delegate in France for the Library of Congress and played an extremely important role in developing cooperation between French and American naval historians in the period leading up to the bicentenary of the United States.
In recognition of her contributions to Franco-American historical relations, she was elected the first woman member of the History, Letters, and Arts section of the Académie de Marine.
After the 1984 discovery of the wreck of CSS Alabama, sunk in Cherbourg harbor during the American Civil War, she helped to organize both the French and American branches of the CSS Alabama Association, serving as president of the French branch and helping to develop support for its work in underwater archeology on the site of the wreck.