She was the eldest daughter of Robert IV de Sablé, and the wife of William des Roches, Seneschal of Anjou, who two years after his marriage to Marguerite became one of the greatest barons in Anjou and Maine, her considerable inheritance having passed to him upon her father's death in 1193.
Marguerite had a brother Robert who died as a child, and a younger sister, Philippa, wife of Geoffroy Marteau.
Her father was a Grand Master of the Knights Templar (1191–1193), and Lord of Cyprus (1191–1192); he was also a wealthy and powerful Angevin baron and landowner.
She brought to William the lordships of Sablé, La Suze, Briollay, Mayet, Loupeland, Genneteil, Precigné, and the Norman manor of Agon; this made him one of the greatest barons in Anjou and Maine.
The Sablé barony and hereditary seneschalship passed on to Amaury I de Craon, husband of Jeanne, the eldest daughter of William and Marguerite.