She began her literary career in 1908 with the publication of her travel memoir Les Huit Paradis ("The Eight Paradises"), which received positive reviews from French critics.

In 1905, when George was sent by the Romanian king Carol I on a diplomatic mission to Mozzafar-al-Din, Shah of Iran, she eagerly embarked on the trip, recording her observations in a journal.

She was awarded the Prix de l'Académie française and met Marcel Proust, who sent her a letter praising her book: "You are not only a splendid writer, Princess, but a sculptor of words, a musician, a purveyor of scents, a poet".

She and her husband were invited to Germany, in the autumn of the same year, as Wilhelm's personal guests, visiting Berlin, Potsdam, Weimar, and taking part in the imperial regatta at Kiel.

In Paris, she also encountered the Roman Catholic Abbé Mugnier, who converted her from her Eastern Orthodox faith, and she began an extensive, frank correspondence with him that was to last 36 years.

Exhausted by many sentimental disappointments, Marthe withdrew to Algeria, then part of the French colonial Empire, to stay with an aunt of her husband, Jeanne Bibesco, thinking about divorcing George and espousing the prince de Beauvau-Craon.

[2] When Romania at last entered the war on the Allied side in 1916, Marthe worked at a hospital in Bucharest until the German army burned down her home in Posada (near Comarnic) in the Transylvanian Alps.

She fled the country to join her mother and daughter in Geneva after a quarantine exile, imposed by the German occupiers, in Austria-Hungary (as a guest of the princely family of Thurn und Taxis at Latchen).

It was Marthe's Romanian masterpiece, where she brilliantly conveyed the everyday life and customs of her people, the extraordinary mixture of superstition, deep philosophy, resignation and hope, and the unending struggle between age-old pagan beliefs and Christian faith.

Among her literary friends and acquaintances, Marthe counted Jean Cocteau, Paul Valéry, Rainer Maria Rilke, François Mauriac, Max Jacob, and Francis Jammes.

During this postwar period she rebuilt Posada, her mountain home, and began restoring the other family estate, Mogoșoaia, a palace built in Byzantine style.

Moving around Europe, acclaimed as she wrote new books – Le Perroquet Vert (1923), Catherine-Paris (1927), Au bal avec Marcel Proust (1928) – Marthe gravitated toward political power more than anything else.

[clarification needed] Without forgetting the former Kronprinz, Marthe had a short love affair with Alfonso XIII of Spain, and another with the French Socialist representative Henry de Jouvenel.

Accompanying George, who was by then interested in fast planes – in addition to his numerous mistresses – Marthe flew everywhere: the United Kingdom (she counted among her friends the Duke of Devonshire Edward Cavendish, the Duke of Sutherland George, Vita Sackville-West, Philip Sassoon, Enid Bagnold, Violet Trefusis, Lady Leslie and Rothschild family members), Belgium, Italy (where she met Benito Mussolini in 1936), the Italian colony of Tripolitania (Libya), Istanbul, the United States (in 1934, as guests of Franklin D. Roosevelt and his wife Eleanor), Dubrovnik, Belgrade and Athens.

Eventually, Valentine and her husband were released from Romanian detention in 1958[clarification needed], and allowed passage to Britain, where Marthe, now totally dependent on her writing for money, bought them a home, the Tullimaar residence at Perranarworthal in Cornwall.

Now a grande dame, she enjoyed her last great friendship with a powerful leader, Charles de Gaulle, who invited her in 1963 to an Élysée Palace reception in the honour of the Swedish Sovereigns.

In January 2001, a national poll of the most influential women in Romania's history placed princess Marthe Bibesco in the first position as the woman of the Millennium and of the 20th century.

Over 350 boxes of Marthe Bibesco's personal papers including manuscripts, correspondence, and photographs are preserved at the Harry Ransom Center at the University of Texas at Austin.