At the age of thirteen Marie-Anne received a marriage proposal from the Count d’Amerval, who was nearly three times her age. Jacques Paulze tried to object to the union, but received threats about losing his job with the Ferme Générale. To indirectly thwart the marriage, Jacque Paulze made an offer to one of his colleagues to ask for his daughter’s hand instead. This colleague was Antoine Lavoisier, a French nobleman and scientist. Lavoisier accepted the proposition, and he and Marie-Anne were married on 16 December 1771.
Over time, she proved to be a scientific colleague to her husband. She translated documents from English for him, including Richard Kirwan's Essay on Phlogiston and Joseph Priestley's research. She created many sketches and carved engravings of the laboratory instruments used by Lavoisier and his colleagues. She edited and published Lavoisier’s memoirs (whether any English translations of those memoirs have survived is unknown as of today) and hosted parties at which eminent scientists discussed ideas and problems related to chemistry.
In 1794 Lavoisier, due to his prominent position in the Ferme-Générale, was branded a traitor during the Reign of Terror by French revolutionaries. Marie-Anne’s father, another prominent Ferme-Générale member, was arrested on similar grounds. On 28 November 1793 Lavoisier surrendered to revolutionaries and was imprisoned at Port-Libre. Throughout his imprisonment Marie-Anne visited Lavoisier regularly and fought for his release. She presented his case before Antoine Dupin, who was Lavoisier’s accuser and a former member of the Ferme-Générale. She told of her husband’s accomplishments as a scientist and his importance to the nation of France. Despite her efforts Lavoisier was tried, convicted of treason and executed on 8 May 1794 in Paris, at the age of 50. Jacques Paulze, Marie-Anne’s father, was also executed on the same day.
After his death Marie-Anne became bitter about what had happened to her husband. She was thrown into bankruptcy following the new government's confiscation of her money and property. In addition, the new government seized all of Lavoisier’s notebooks and laboratory equipment. Despite these obstacles, Marie-Anne organized the publication of Lavoisier’s final memoirs, Mémoires de Chimie, a compilation of his papers and those of his colleagues demonstrating the principles of the new chemistry. The first volume contained work on heat and the formation of liquids, while the second dealt with the ideas of combustion, air, calcination of metals, action of acids, and the composition of water. In the original copy Marie-Anne wrote the preface and attacked revolutionaries and Lavoisier’s contemporaries, whom she believed to be responsible for his death. This preface, however, was not included in the final publication. Nevertheless, her efforts secured her husband's legacy in the field of chemistry.