Why does Grete all of the sudden start playing her violin now?

Grete begins playing her violin as a way to express her emotions and cope with the family's increasingly dire situation. The act of playing serves as a form of escape and a means to reclaim her identity, which has been overshadowed by Gregor's transformation and the family's struggles. Additionally, it reflects her desire for normalcy and connection amidst the chaos, showcasing her development as a character.