Her younger brothers included Charles, Duke of Mayenne (1554–1611) and Louis II, Cardinal of Guise (1555–88).

"[4] In July 1587 a board was erected in the cloister of Saint Sévérin that represented the sufferings of Catholics under Queen Elizabeth I of England.

It was generally thought that Catherine de Montpensier was responsible for the board, which was viewed by many people each day.

The board probably used images from the Theatrum Crudelitatum haereticorum nostri temporis of Richard Rowlands, who had been paid large sums of money by King Philip II of Spain for activities that would undermine support for Henry III.

The Library of the Duchess of Montpensier, published in 1587, tried to discredit her and other women of the court with a satirical list of imagined titles that implied sexual voracity and infidelity.

One was entitled "Inventory of the Proportions of French Cocks, with the Great Balls of Lorraine, by Madame de Nermoutier.

According to Pierre de L'Estoile she bribed the preachers and curates to convey her message with money and offers of bishoprics, abbeys and other valuable offices.

The next day Catherine's younger brother Cardinal Louis II was also assassinated at the Château de Blois.

[2] According to Paul Lacroix, The man who brought the first news to the Duchess of Montpensier (Catherine Marie de Lorraine) and her mother, Mme de Nemours, was received as a saviour; the duchess flung her arms round his neck and kissed him, crying, ' Ah, my friend, welcome!

In 1593 Charles of Mayenne convoked the States-General in Paris and tried unsuccessfully to be elected King of France with Catherine's support.

The leading noblemen supported the coronation, and on 22 March 1594 Henry IV entered Paris in triumph.

[8] After Paris surrendered on 22 March 1594 she asked if there was someone who would stab her in the breast, but as soon as he entered the city Henry IV sent her greetings and told her she was under his personal protection.

Pierre de L'Estoile wrote in his diary that he was sure this was caused by the passing of her malignant and tempestuous spirit.