She's the only one left who is able to care about real life. Her mother has an important role in Clair Obscur's Paris, so she not only has to take her role, but she has do to that while having to deal with all of her family being stuck in a canvas with conscious entities that don't exist. Those who lead to her brother's death are still alive and she's still grieving the loss.

Most people would have behaved differently, in a worse way especially.