Desperately in love with the adventurer Riviére, who demanded money from her, she made several attempts to murder her husband, once by the use of poison acquired from Marie Bosse.
Marguerite de Poulaillon was the first person from the upper classes to be implicated in the Poison Affair, and the case against her was expected to form a precedent against others accused of similar social status, and was therefore carefully treated.
However, according to Gabriel Nicolas de la Reynie, she was unsatisfied with the sentence, perhaps because she feared being put under the guardianship of her husband, and asked to be imprisoned, as she would otherwise be inclined to repeat her crimes.
In 1697, Marguerite de Poulaillon appealed to be transferred from the work house to a convent, but her appeal was denied by Gabriel Nicolas de la Reynie, and she remained in the prison work house until her death.
It also affected the verdicts of other accused based on rank: Francoise de Dreux and Marguerite Leféron, the former guilty of several murders and the latter to the murder of her husband to marry her lover, were both Parisian socialites and were both merely sentenced to exile from Paris, while the wife of court musician Philippe Rebille Philbert, who poisoned her first husband to marry Philbert, was hanged for the same crime.