[6] Marie's dowry was to be 100,000 francs, but her father never paid the entire amount, creating tension between the duchies of Brittany and Alençon in later years.
Marie and her husband John had five children:[8] In January 1414, Charles VI of France raised the county of Alençon to a duchy, and made Marie's husband, John, the first duke of Alençon.
[11] Marie's husband died at the Battle of Agincourt, where he fought alongside the King of France.
[12] After the death of her husband in 1415, Marie was forced to flee Normandy, where she had been living prior to the Battle of Agincourt.
Much like Gisela of Aquitaine, Mahout of Artois, and her own great-niece Margaret of Brittany, Marie was both literate and the owner of at least a Book of Hours.