She was born into the
House of Castro as the daughter of
Pedro Fernández de Castro and
Isabel Ponce de León. She was the sister of
Fernando Ruiz de Castro and the half-sister of
Inês de Castro and
Álvaro Pires de Castro. Among her advisors were her uncle-in-law
Enrique Enríquez the Younger and . In 1354, after the death of her husband Diego López de Haro, with whom she had a son, she met
Peter of Castile. He was attracted to her beauty and Sanabria arranged a marriage. Historian argued that Castro agreed to marry Peter out of ambition rather than love. As told by
chronicler Pero López de Ayala: Castro demanded Peter to nullify his marriage with
Blanche of Bourbon; he complied and had bishops and carry out the act. In early April, they married at
Cuéllar and as a part of her
dowry she received , , and
Dueñas Castle. She was pronounced Queen of Castile, though the marriage lasted one day before Peter left her. She was pregnant with their son, John (1355–1405). The only estate she was left with was Dueñas Castle, retiring to the
corresponding town. On 21 August 1374, she died in Dueñas. Her tomb is in the
Santiago de Compostela Cathedral. ==References==