Her father was the distinguished Spanish diplomat and scholar Salvador de Madariaga. Her mother was the distinguished economic historian Constance Archibald.

Nieves's sister Isabel de Madariaga (1919 - ) became Professor of Slavonic Studies at the University of London.

She was employed for upwards of 20 years by the Food and Agriculture Organisation, a United Nations agency headquartered in Rome. Her Yale University-published book on the life of Sir Francis Bacon was released in 1996. The 606 page volume is called Francis Bacon: The History of a Character Assassination. She claimed in her acknowledgements that the book was suggested and blessed by "my teacher, Osho" (Bhagwan Shree Rajneesh), "who thought highly of Sir Francis Bacon and gave the book his blessing." She was also deeply influenced by the works of Immanuel Velikovsky. In her earlier years, 1956, she wrote a crime novel, She Died Without Light.