Beatrice was raised in the castle of Infante John, Lord of Reguengos de Monsaraz. In 1447 Beatrice accompanied his daughter, Princess Isabel of Portugal, to Castile as her lady-in-waiting when Isabel left to marry King John II of Castile and became Queen of Castile and León. Beatrice was her good and close friend, (and later was to receive her support when she founded the Conceptionists). Soon, however, her great beauty began to arouse the irrational jealousy of the Queen, who had her imprisoned in a tiny cell. During this incarceration, Beatrice experienced an apparition of the Blessed Virgin Mary, in which she was instructed to found a new Order in Mary's honor.