Like her sister, Louise, Queen consort of Prussia, she failed in their negotiations with Napoleon I of France, but during the Congress of Vienna, she was successful in enforcing the interests of the Thurn and Taxis family.

[5] Only with the predictable demise of the Imperial Reichspost, the German Mediatisations of 1803, the mediatization of the Princely House of Thurn and Taxis, and the loss of position of Post Master General in the time of Napoleon I of France, Therese became outwardly politically active, most especially after the death of her father-in-law in 1805.

In 1806, she and her husband negotiated with her brother-in-law Frederick William III of Prussia along with Karl Theodor Anton Maria von Dalberg, the former Archbishop-Elector of Mainz and Prince-Primate of Regensburg, and for the first time in 1807 with Napoleon.

[6] After fruitless negotiations in Erfurt were lost, Therese traveled at the end of 1809 to Paris, where she met with Napoleon concerning the future status of the Princely House of Thurn and Taxis, the withdrawal of the media, and the re-acquisition of rights to the postal system.

Not least because of Article 17 of the Federal Act from the year 1815, the revenue of the former post offices of the House of Thurn and Taxis in several states of the German Confederation as a legitimate claim was established.