In the summer of 2012, Joosje performed at Dutch Theatre Festival The Parade (De Parade) as Snow White in the show All Fairytales: Snow White (Allemaal Sprookjes: Sneeuwwitje) by youth theatre school Rabarber. The show was performed in The Hague and Amsterdam, directed by Rebecca van Leeuwen.
Joosje started acting when she was 7 at youth theatre school Rabarber, where she had classes in acting and dancing for over ten years. She had roles in multiple shows, and performed in Charlie and the Chocolate Factory as Veruca in Theater aan 't Spui in The Hague, directed by Wim Serlie.
After Rabarber, Joosje had methoc acting training at The Lee Strasberg Theatre and Film Institute, as well as classes in Performing Comedy, Downtown Theatre, Acting for the Stage and Screen & Voicing the Text at New York University.