Blanceflor was born in Rome in 1891, the daughter of the Swedish baron Carl Bildt and his wife Alexandra Keiller. Blanceflor's grandfather, Gillis Bildt, had been Prime Minister of Sweden. Her father, Carl Bildt, was minister at the Swedish Embassy from 1889 to 1920. He was also a successful historian and writer, was elected to the Swedish Academy and awarded an honorary doctorate, and even had the honour of having a street in Rome named after him: Via Carlo de Bildt. He stayed on in Rome until his death in 1931.

Blanceflor received a broad education, growing up in a home very much a part of the rich cultural life of the Rome of that time. She was fluent in Italian, French and English, and although she lived in Sweden only for short periods, also spoke excellent Swedish.

When she was 20 or so, she and a young Italian prince fell in love. His name was Andrea Boncompagni-Ludovisi, and they decided to marry. But oh no, in those days and in those circles these things were not so easy. The prince's family had already come to an arrangement with a very rich American family, Preston. The young prince should marry their daughter Margeret. The agreement was that if the couple had no children, and should the prince wish it, the marriage would be dissolved after 10 years, Margeret would keep her title Princess, while the prince would receive the income from two large trusts in America. The marriage indeed proved to be childless, was dissolved, and in 1924 Andrea married Blanceflor, who had waited 10 years for her prince. The marriage was a happy one.

They had no children. When Prince Andrea died in 1948, Blanceflor inherited the trusts, as well as the house where she lived, 18 Via Boncompagni in Rome, and an estate in Umbria. She also bought a villa, La Sosta, in the Albaner mountains. Her life style was that of an earlier age.

Blanceflor died in 1972 and was buried beside her parents in Rome. But she had already in 1955 established a foundation for research and education to which she gave her name. During her life-time, the foundation was modest, but she left a significant part of the American funds as well as assets in Switzerland and Sweden to the foundation.