Born in Santarém,[1] when Blanche was two years old, her father gave her, as a perpetual donation, the city of Montemor-o-Velho with the condition that it would revert to the crown upon her death or in the event that she married outside of Portugal.

[2] There is documentary proof that mother and daughter were living in 1283 in Seville with the king[4] who in his will mentioned his granddaughter Blanche and left her a substantial sum for her marriage.

On 27 September 1305, she purchased for 170,000 maravedíes from Juana Gómez de Manzanedo, the widow of infante Louis, son of Ferdinand III of Castile, her inheritance in the city of Briviesca.

[6] She is considered the founder of the city as its sponsor and coordinator, and was also responsible for the founding of Colegiata de Santa María.

[8] She executed a will on 15 April 1321[9] where she ordered her burial at the Convent of Las Huelgas[10] and also asked that ten thousand masses were to be celebrated for the good of her soul.