On 6 November 1779, eighteen-year-old Dorothea became the third wife of the 55-year-old, childless Duke Peter von Biron, son of the famous Ernst Johann von Biron. The couple had six children, two of whom died in infancy. The four surviving children were all daughters; however, the youngest one, Dorothea, was probably illegitimate, although recognized by the Duke. Dorothea was welcomed into the highest social circles thanks to her new status as duchess as well as her beauty. Because her husband was preoccupied with political difficulties at home involving his overlord the King of Poland and the Courland nobility, he frequently sent her on diplomatic missions to Warsaw, lasting months at a time, and to Berlin, Karlovy Vary, and Saint Petersburg for shorter periods. During these long absences Dorothea became alienated from her husband and had numerous love affairs with other men, including Gustaf Mauritz Armfelt, Talleyrand, and the Polish nobleman, Count Alexander Benedykt Batowski, who allegedly fathered her fourth daughter, born in 1793. After the year she gave birth to her illegitimate daughter, also named Dorothea, the Duchess moved permanently to the :de:Palais Kurland|Palais Kurland in Berlin, where she held an aristocratic salon.
Later life
In 1794 she acquired the Gutsherrschaft Löbichau in Altenburgischen and spent her summers at the newly built Schloss there. Inviting poets, philosophers, relatives and friends to Löbichau, it became known as the Musenhof der Herzogin von Kurland. Her sister Elisa von der Recke, who would later be linked with Christoph August Tiedge, came to Löbichau to live and Tsar Alexander I of Russia, Frederick William III of Prussia, Napoleon I of France, Talleyrand, Metternich, Goethe, Schiller and other personalities of the time were the duchess's personal friends. In 1801, she received a proposal from Prince Frederick Adolf of Sweden. Upon her youngest daughter Dorothea's marriage to Talleyrand's nephew, Edmond de Talleyrand-Périgord, in 1809, the duchess moved to Paris, having an intense relationship with Talleyrand and influenced him to turn against Napoleon. In 1814 she traveled to the Congress of Vienna to confront him about his alleged love affair with her daughter Dorothea. A few years after her death at Löbichau in 1821, the Duchess' body was moved from her place of death to the family vault at Sagan where her husband was buried in 1800.