- Daughter of Álvaro Perez de Castro, Count of Arraiolos, first constable of Portugal, and his wife María Ponce de León.
- Lady-in-waiting to Beatriz of Portugal, second wife of Juan I of Castile, when they went to Portugal to claim the crown in 1383. [João1, ch. 64]
- With the aid of Alfonso Enríquez and his brother Count Pedro, a cousin of Juan I of Castile, she tried to plot Queen Leonor Teles' escape from Juan's captivity. [João1, ch. 79]
- During the siege of Lisbon, 1384, she married Pero Núñez de Lara, Count of Mayorga, but was widowed shortly afterward, as her husband was killed by the plague. [João1, ch. 141, 149, 166]
- Appointed lady-in-waiting to Queen Philippa of Portugal, when King João I established the queen's house, in whose service she received the monthly sum of one thousand pounds. [João2, ch. 129]
- King João I proposes her marriage to the Constable Nuno Álvares Pereira but, with his wife recently deceased, he was upset by this proposal and asked permission to leave the Court. [João2, ch. 131]
- King João I expelled her from the Portuguese court owing to her forbidden relationship with Fernando Afonso, his camberlain. [João2, ch. 139]
Breatiz