“In Montmorency [Quebec], the ghost is thought to be Mathilde Robin. In 1759, in the middle of the Seven Years War, Mathilde had found her true love in Louis Tessier, a local farmer and member of the militia who asked for her hand in marriage. Her father approved of the match and the two were to be married at the end of the summer in 1759.
“However, this was a turbulent time in Québec and Louis was soon sent to fight in the Battle of Beauport, which took place at the base of the Montmorency Falls on July 31, 1759.
“The English forces were controlled by General James Wolfe who is famous for taking Québec during the Plains of Abraham. He would not be victorious during this battle; wet air from the falls and a sudden storm ruined the English gun power and the British troops were forced to retreat. Wolfe recorded 210-deaths in this journal. The French leader, Louis-Joseph de Montcalm, recorded 60.
“However, for poor Mathilde, the French were victorious but her beloved Louis was one of the 60-militiamen who were killed. In her grief, it’s believed that she put on her wedding dress and threw herself from the top of the falls, where they had met the evening before. People have claimed to have heard her cries or to have seen her ghost in a white dress falling from the top of the falls.”
From The Travel Geek: Montmorency: La légende de la Dame blanche
The Devil's Muse 