When Marie was 18, she was married to a Breton nobleman, Henri, Marquis de Sevigne, who, like her father, had a good name but little wealth. During their six years of marriage, the couple divided their time between Paris and their Brittany home, and a daughter and a son were born. Luckily, the Abbe de Livry soon arranged a legal partition of the couple's properties; the marquis spent his money on his mistresses and in 1651 was killed in a duel over one of them.
Widowed at 26, Sevigne spent most of her time in Paris, where she became a popular member of the salons and the court, considered as a especially witty conversationalist. She became a close friend of the Comtesse de La Fayette, eight years younger but whom she had known for years. During the 1650s and 1660s, Sevigne had several offers of marriage, which she declined. Her goal was to educate and then to establish her children: to marry her daughter well, which would require a large dowry, and to spend what would be necessary to get her son a good army commission.
The letters that Sevigne wrote during these years, to friends and relatives away from Paris, reveal the wit for which she was praised, and many were saved by their recipients. Her reports on the 1664 trial of the financier (and friend) Nicolas Fouquet, are so detailed that they have become part of the historical record of the period. Her letters to her cousin Bussy --- first at war, later in exile from the court --- are perhaps more revealing of her own feelings; the cousins would frequently quarrel but always return to sharing their thoughts with one another.
By 1669, Sevigne's son, Charles, had his commission; and her daughter, Francoise, was married to the Count de Grignan, from one of the noblest family of Provence. The count was in Paris and expected to get a position at court, which is exactly what Sevigne had planned. She always understood that a son in the army would have to go away, but she assumed that her daughter would remain near her. In this assumption, she was wrong: Louis XIV appointed Grignan as Lieutenant Governor of Provence, an honor, but an expensive one --- and one that would require him and his wife to live far from Paris.