Primarily known for her work in French cinema, she also made waves internationally, notably starring as police officer Laurence Relaud in the BBC series "The Missing." "Rosetta," directed by cinema giants Luc and Jean-Pierre Dardenne, portrayed a gripping tale of resilience, and Dequenne's performance was praised for its authenticity. The Dardenne brothers acknowledged her remarkable talent, stating, "She was magnificent, and the film owes a lot to her."

Throughout her career, Dequenne appeared in various significant films, including "La fille du RER" (2009), "Pas Son Genre" (2014), and the 2022 Cannes nominee, "Close." Following her passing, tributes poured in, including a heartfelt message from French Minister of Culture Rachida Dati, who lamented the loss of such a vital talent in Francophone cinema.

In October 2023, Dequenne revealed her diagnosis of adrenocortical carcinoma (ACC), a rare but aggressive cancer of the adrenal glands. In a touching Instagram post for World Cancer Day, she reflected on the challenges ahead, writing, “What a tough fight! And we don’t choose…” Her passing leaves a void in the film industry, but her legacy will resonate through her impactful performances and dedication to the craft.