After she entered Parliament, Dubost served as one of four deputy chairpersons of the LREM parliamentary group alongside Pacôme Rupin, Danièle Hérin and Gilles Le Gendre under the leadership of group president Richard Ferrand (2017–2018). In 2018, she supported Laetitia Avia to become group president, a position Le Gendre was elected to.[6] She serves as Vice President of the Committee on Legal Affairs.[7] In addition to her committee assignments, she is a member of the French-Chinese Parliamentary Friendship Group.
In May 2020, Dubost joined En commun (EC), a group within LREM led by Barbara Pompili.[8]
In September 2020, Dubost was a candidate to succeed Le Gendre as parliamentary group president; she came in fourth. In the final round of the vote, she endorsed Christophe Castaner, who appointed her as one of his deputies alongside Aurore Bergé.[9]
In 2019, Dubost steered through Parliament a bioethics law extending to homosexual and single women free access to fertility treatments such as in vitro fertilisation (IVF) under France's national health insurance; it was one of the campaign promises of President Emmanuel Macron and marked the first major social reform of his five-year term.[11]