Dubois translated work by the French writer Françoise Sagan. In addition, Dubois wrote in Dutch and French for the publisher of the magazine Libelle, also based in Haarlem.[1][5]
When her children were adults, she began to do even more research and wrote more often. In 1952, after a suggestion from her husband[4] she discovered the work of Belle van Zuylen (1740–1805), the Dutch writer who wrote in French, after reading a biography by Philippe Godet. She wrote a biography of Van Zuylen herself (published in 1969), and translated her work, among other things the anthology of letters Rebels en beminnelijk (published in 1971).[6]
Publisher G.A. van Oorschot wanted to publish the Collected Works and the biography of Belle van Zuylen with a subsidy from the Netherlands Organisation for Scientific Research. However, the subsidy application was rejected twice. The Dubois couple had no academic education.[7][8][9] On the advice of Leendert Brummel, emeritus professor of Library Science at the University of Amsterdam, Dubois became a member of the 18th Century Working Group in February 1970 in order to get to know other people interested in Van Zuylen, better known in French by her married name as Isabelle de Charrière. In September 1973, Dubois became secretary of this working group. With the working group, she organised the international congress Actualité d'Isabelle de Charrière in Zuylen Castle in September 1974. This led to the creation of the international editorial team, of which Simone Dubois was general secretary, which ultimately led to the publication of the collected works of Belle van Zuylen in 10 volumes on thin paper in the period 1979–1984.[10] Simone and Pierre Dubois were members of the editorial team of this publication by publisher Van Oorschot. With this, Simone Dubois became 'the driving force behind the development of Belle de Zuylen's work'.[11]
In 1974, Simone and Pierre Dubois also co-founded the Belle de Zuylen Society with the annual magazine Lettre de Zuylen, the first edition of which was published in 1976.[12][13] In 1990, she and her husband retired as board members of the Belle de Zuylen Society to fully focus on writing the biography.
In 1984, Dubois published an article about Anna Maria van Schurman.
Eventually, together with her husband, she wrote the more extensive biography of Belle van Zuylen, Zonder Vaandel (published 1993), based on the Collected Works and their research. Dubois was already 83 years old at the time. This biography became a success and ended up on bestseller lists.
When her husband died in 1999, she mainly took care of his literary legacy.[4]