As soon as the first signs of the Fronde broke out, Mme. de Chevreuse became active and succeeded in attracting to her the young Marquis de Laigues with whom, later on, she contracted a _mariage de conscience_. As ambassador of the Fronde, she prevailed upon Spain to promise troops and subsidies to her party. After the peace of 1649, she went to Paris where she found almost all her friends ready to follow her and to pay her homage. It was she who conceived the idea of an aristocratic league which, under the auspices of the two great princes of the blood, the Duke of Orléans and the Prince of Condé, would unite the best part of the nobility.
Her plan was to marry her daughter to the Prince de Conti and the young Duc d'Enghien to one of the daughters of the Duke of Orléans. The contracts were signed and all was in readiness when Mazarin was exiled, and the following Frondists came into power: the Duke of Orléans at court, Condé and Turenne at the head of the army, Châteauneuf in the Cabinet, Molé in Parliament, while Mme. de Chevreuse and Mme. de Longueville managed to keep harmony among all. Queen Anne in a short time annulled the marriage contracts; and on the return of Mazarin, Mme. de Chevreuse took up her work with him, the cardinal being wise enough to appreciate the fact that she was a greater force with than against him.
Strange as it may seem, Mme. de Chevreuse in time became the great acting and controlling force of royalty, winning over the Duke of Lorraine and becoming a staunch friend to both the regent and the cardinal; after the death of the latter, she became all-powerful, and it may be said that she made Colbert what he was. In the fulness of her power, she gradually retired, having seen, in turn, the passing away or the fall of Richelieu, Mazarin, Louis XIII., Anne of Austria, the Queen of England, Châteauneuf, the Duke of Lorraine, her daughter, and the Marquis de Laigues. She ceased plotting, renounced politics and intrigues, and retired to the country, where she died in 1679.
Mme. de Chevreuse was undoubtedly one of the most important political characters of the seventeenth century, just as she was also one of its greatest beauties--possibly the most seductive and charming woman of her epoch. A consummate diplomat and an untiring worker, she was at the head of more intrigues and plots, had more thrilling adventures, controlled and ruined more men, than any other woman of her century, if not of all French history. Thinking little of religion, she was yet in the very midst of the Catholic party; unswerving in her friendships, she scorned danger, opinion, fortune, for those whom she loved or whose cause she espoused; an implacable foe, she was the most dreaded enemy of both Richelieu and Mazarin.