Ileana was born in Bucharest on 5 January 1909, the youngest daughter of Queen Marie of Romania and King Ferdinand I of Romania. Although it was rumored that Ileana's true father was her mother's lover, Prince Barbu Ştirbey, the king admitted paternity.
In Sinaia on 26 July 1931, Ileana married the Archduke Anton of Austria, Prince of Tuscany. This marriage was encouraged by Ileana's brother, King Carol II, who was jealous of Ileana's popularity in Romania and wanted to get her out of the country. After the wedding, Carol claimed that the Romanian people would never tolerate a Habsburg living on Romanian soil, and on these grounds refused Ileana and Anton permission to live in Romania.
After Michael I of Romania abdicated, Ileana and her family were exiled from the newly Communist Romania. The years from 1950 to 1961 were spent lecturing against communism, working with the Romanian Orthodox Church in the United States, writing two books: I Live Again, a memoir of her last years in Romania, and Hospital of the Queen's Heart, describing the establishment and running of the hospital.
On 29 May 1954, Ileana and Anton officially divorced and she married secondly in Newton, Massachusetts, on 20 June 1954, to Dr. Stefan Nikolas Issarescu (Turnu-Severin, 5 October 1906 - Providence, 21 December 2002).
In 1961, Princess Ileana entered the Orthodox Monastery of the Protection of the Mother of God, in Bussy-en-Othe, France. Her second marriage ended in divorce in 1965. On her tonsuring as a monastic, in 1967, Sister Ileana was given the name Mother Alexandra. She moved back to the United States and founded the Orthodox Monastery of the Transfiguration in Ellwood City, Pennsylvania, the first English language Orthodox monastery in North America.
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In January 1991, she suffered a broken hip in a fall on the evening before her eighty-second birthday, and while in hospital, suffered two major heart attacks. She died four days after the foundations had been laid for the expansion of the monastery.