Madame de Saint-Laurent was born on 30 September 1760 in Besançon, France, to Jean-Claude Mongenêt, a civil engineer, and Jeanne-Claude (Claudine) Pussot.

Madame de Saint Laurent lived with him at the Duke of Kent House in Quebec City for three years before he was posted to Halifax, Nova Scotia, in 1794.

[1] Recent scholarship (particularly by Mollie Gillen, who was granted access to the Royal Archive at Windsor Castle)[2] has established that no children were born of the 27-year relationship between Prince Edward and Madame de Saint-Laurent; although many Canadian families and individuals (including the Nova Scotian soldier Sir William Fenwick Williams, 1st Baronet)[3] have claimed descent from them, such claims can now be discounted in light of this new research.

[1] For twenty-eight years Madame de Saint-Laurent presided over the Duke's household, as a local chronicler records, "with dignity and propriety".

After the Duke's marriage in 1818 to the Dowager Princess of Leiningen, Madame de Saint-Laurent retreated to Paris where she lived out her days amongst her family and friends.