This is one I forgot to add last month. Madame Lafarge (born Marie Cappelle in 1816) was known as 'the poisoner of Tulle' for killing her husband with arsenic in 1840. She served part of her sentence in Montpellier, and was interned in Saint-Paul-de-Mausole psychiatric hospital in St-Rémy-de-Provence (where Van Gogh stayed later) for fifteen months (1851-2). Suffering with tuberculosis, she was released and died in Ussat-les-Bains (Ariège) in November 1852. There are very serious doubts as to whether she did in fact poison her husband.
Marie Cappelle was also a writer of talent and over some years wrote a series of memoirs, most published in her lifetime and a few posthumously.