Marie Guers was born in La Léchère, Savoie, Auvergne-Rhône-Alpes, France, on 30 August 1914. She was the daughter of Italian immigrants from Favaro, Piedmont. Her older brother, Aldo, was born in Italy. Her father initially worked as an electrical fitter. The family then moved to Crolles, and later, they relocated to La Terrasse, where her father established a bicycle and motorcycle repair business. Marie became fluent in Italian, a skill she regretted not being able to use with friends in later life. She had learned the language while attending school in Italy, where she had returned to care for an elderly aunt.

In 1939, she married Louis Guers, who had studied at an agricultural school and became the manager of the La Terrasse wine cooperative, built in 1936. Like many women in La Terrasse and the Grésivaudan Valley, Marie made gloves as part of her work. The couple had two children, and by the age of 106, she was also a grandmother to two and a great-grandmother to three.