On 8 October 1839, Valentine was married to Alexandre Edmond de Talleyrand-Périgord, 3rd Duke of Dino, at the Château de Beauregard at Cellettes (Loir-et-Cher), her mother's property.
Valentine's passionate admirer, Anatole Demidov, attended her wedding and even helped assist the event. He offered her a diamond ornament whose magnificence caused the bridegroom worry.
The next year, in 1840, Demidov briefly broke off their liaison due to financial problems, but later that same year married Mathilde Bonaparte and resumed his affair with Valentine on his first stay in Paris after his wedding.
In 1845, he arranged for Valentine to settle with him in Florence and stayed by her side, even though her husband took umbrage. At a costume ball, Valentine was insulted by her rival, Mathilde, and in response Demidov slapped his wife twice in public, which signalled their final separation soon thereafter.