Their claim to the throne of Achaea came from her great-grandfather Philip of Savoy, eldest son of Thomas III of Piedmont and Guia of Burgundy. Philip married Isabella of Villehardouin, Princess of Achaea and co-reigned with her from 1301 to 1307. They were both deposed by Philip I of Taranto but continued to claim the title. However Giacomo was a son of Philip by his second wife Catherine de la Tour du Pin and his claim to be the heir of Isabella of Villehardouin was disputed.
On January 17, 1403, Margaret married Theodore II, Marquess of Montferrat, a member of the Palaiologos dynasty and male-line descendant of Andronikos II Palaiologos. Theodore was the widower of Jeanne of Bar, daughter of Robert I, Duke of Bar and Marie Valois.
This marriage lasted for fifteen years but was childless. Theodore died in 1418.
Her piety, already great, increased after she had heard the preaching of Vincent Ferrer, who spent several months in Montferrat. Therefore, when she was left a widow in 1418, she decided to abandon the world. Leaving the direction of the affairs of the marquisate to Jean-Jacques, the son of her husband by his first marriage, she retired to Alba where she joined the Third Order of St. Dominic.
A little later, Filippo Maria Visconti, Duke of Milan, asked her hand in marriage and begged Pope Martin V to relieve her of her vow. But Margaret opposed a formal refusal to this request and thoroughly resolved to give herself entirely to God: with several young women of rank, she founded a monastery and placed it under the rule of the order of St. Dominic. Redoubling her mortifications she remained a model of piety and died in a saintly manner at Alba, 23 November, 1464.