She was a daughter of Prince Ivan Ivanovich Baryatinsky (1772–1825), a member of one of the most influential families of the Russian nobility, and son of Princess Catherine of Schleswig-Holstein-Sonderburg-Beck.

On 23 October 1834, Leonilla married her cousin and one of the Tsar's aides de camp, Prince Ludwig zu Sayn-Wittgenstein-Berleburg-Ludwigsburg (1799–1866), at Castle Marino, Kursk Governorate.

[1] Leonilla and Ludwig had four children: Her beauty created an impression at the Russian court, but her husband fell from favor, perhaps because his liberal treatment of his serfs.

Ludwig received, as a present from King Friedrich Wilhelm IV of Prussia, the former family seat Sayn Castle, which had been destroyed in the Thirty Years' War.

[citation needed] Ludwig and Leonilla owned the former Baroque manor of the Counts of Boos-Waldeck below Sayn Castle reconstructed into a princely residence in Gothic Revival style.

Their youngest son Alexander married Yvonne, daughter of the French Duke of Blacas, and inherited Sayn after the morganatic marriages of his older brothers Peter, Friedrich and Ludwig.

[4] In 1876, at a time when the exercise of the Catholic faith was not yet fully authorized in the canton of Vaud, she built on her property a private chapel, which became in 1912 the parish church of the Sacred Heart of Ouchy.

[1] She appears reclined on a low Turkish sofa on a veranda overlooking a lush tropical landscape, possibly the Wittgenstein palace in the Crimea, even though the portrait was painted in Paris.

Winterhalter contrasted the sumptuous fabrics and vivid colors against the princess's alabaster flesh to heighten the sensuality of the pose, the model, and the luxuriant setting.