On 22 December 1726, Maria Margarida married her uncle, Joaquim Francisco de Sá Almeida e Menezes, 2nd Marquis of Abrantes (her mother's younger brother), who died in 1756.
King Joseph I of Portugal elevated the dowager marchioness to the title and degree of Duchess of Abrantes vitalício (by Royal Decree of 1757) upon her appointment as the Queen's Mistress of the Robes (Camareira-Môr (in Portuguese)).
This was the highest position in the Portuguese court for a lady, and one which her mother previously held.
On 20 February 1757, she married secondly João da Bemposta, natural son of the Infante Francisco, and her husband was raised to the style and degree of duke on 18 May 1757.
This biographical article about a member of the Portuguese nobility is a stub.