Spanish religious and mystical writer, declared Venerable by Clement X. He/She was born and died in Ágreda (Soria). Only daughter of an accommodated marriage and of Jewish origin, transformed his house into a convent in 1618, after having votes since his childhood and experience numerous visions, mystical, more intense and frequent since its entry into life of religion in 1620. He/She wrote mystical city of God, miracle of his omnipotence and abyss of grace. Divine history and life of the Virgin, mother of God... manifested by the same lady to his slave sister María de Jesús, a biography of the Virgin where defends with determination the dogma of the Inmaculada Concepción; his confessor forced him to destroy this work, but finally saw the light, and posthumous, in 1670. Certain traits heterodox, quietist, passed to the Index librorum prohibitorum (1681) and received harsh criticism from French intellectuals. There are doubts about individual authorship of the work. However, more interest has aroused his correspondence with Felipe IV following a visit by the monarch to the monastery in 1643, attracted by his reputation as a holy and wise. Since that time, the epistolary relationship between the monarch and the nun turned it into a kind of private counselor to 1665, the year in which they both died. Deserves special attention a letter of October 13, 1643, where sor María tells the King that, after the fall of Olivares, must exercise their functions in person, without distinguishing any Minister in particular. To give more force to his warning, sor María gave to understand that breach of this divine duty would constitute a serious risk to his soul. He/She also wrote spiritual scale up to perfection and laws of the wife.