minority was 21 until the 1970s here, so yes, would be a minor.
As far as the marriage with Joseph Carpentier, it's her sister, baptized Marie Adèle that one, b 24 Jul 1818 bapt. 25th in La-Baie-du-Febvre. She is cited of age on the 1844 marriage with Joseph.
It's actually frequent enough that women used another name or a nickname in adult life.