She played a central role in the Spanish royal court during the first years of the reign of Philip V, until she was ousted from the country following a power struggle with the new queen consort, Elisabeth Farnese.

The marriage was far from harmonious, but her husband left her his fortune (popular imagination thought it to be huge, but in reality, the duke was almost bankrupt) and the leadership of the French party in Rome.

She had indulged in much unofficial diplomacy at Rome, particularly with Neapolitans and Spaniards of rank, whom it was desirable to secure as French partisans in view of the approaching death of Charles II of Spain, and the plans of Louis XIV to place his family on the Spanish throne.

During the worst times of the War of the Spanish Succession, she was the real head of the Bourbon party and was well aided by Princess Maria Luisa of Savoy, the spirited young queen of Philip V. She did not hesitate to quarrel even with so powerful a personage as Cardinal Luis de Portocarrero, Archbishop of Toledo, when he proved hostile.

Yet she was so far from offending the pride of the nation that, when in 1709 Louis XIV, severely pressed by the other Great Powers, threatened or pretended to desert the cause of his grandson, she dismissed all Frenchmen from the court and threw the king on the support of the Castilians.

Madame des Ursins confesses in her voluminous correspondence that she made herself a burden to the king in her anxiety to exclude from him all other influence, watching him as if he were a child.

Madame des Ursins, who had gone to meet the new queen at Quadraque near the frontier, was driven from her presence with insult and sent out of Spain without being allowed to change her court dress, in such bitter weather that the coachman lost his hand by frostbite.

After a short stay in France, she went to Italy, eventually establishing herself in Rome, where she imposed her personality on the small émigré Jacobite court of "The Old Pretender", effectively running it until she died on 5 December 1722.

[1] Madame des Ursins has the credit of having begun to check the overgrown power of the church and the Inquisition in Spain, and of having attempted to bring the finances to order.