Démosthène was born in the United States and raised between Port-au-Prince, Haiti and New York.

Démosthène earned her Bachelor of Fine Arts from Parsons the New School for Design in New York and her Master of Fine Arts from Hunter College-City University of New York. She has exhibited extensively through group and solo exhibitions in the United States, the Caribbean, the United Kingdom, Europe and Africa. Démosthène’s solo-presentation with Mariane Ibrahim at The Armory Show 2019, named her a top pick at the fair in the New York Times. She is the recipient of the Tulsa Artist Fellowship, Arts Moves Africa Grant and the Joan Mitchell Foundation Grant. Her work can be seen at the University of South Africa (UNISA), Lowe Museum of Art and in various private collections including the Hessel Museum of Art.