Her father had died by 1194 and she was his heiress, bringing to her husband her ancestral lands of Dendermonde, Meulebeke, and Lokeren, as well as the hereditary office of advocatus of the Abbey of Saint Bavo at Ghent.

[3][4][2] When her husband died in 1214, the Count of Flanders was at war with the King of France and the town of Béthune was in the hands of French troops.

As her eldest son Daniel was still under age, the commander of the French forces put Matilda in charge of the town.

She assumed her late husband's titles, calling herself advocatus of Arras until 1216, when Daniel had reached age 21 and become Lord of Béthune.

She however remained Lady of Dendermonde and advocatus of Ghent, defending her hereditary rights against challenges.