Is a sick daughter's prayer for the death of her father, who is causing her and her mother distress, considered a sin, and what is the expiation for this sin?

A woman's saying "this is a mistake" is understood as a kind of objection to God's decree and a sign of discontent with it. She must repent and seek forgiveness. It is also preferable for her to give charity along with her repentance, for charity extinguishes sin. As for supplicating for a sick person to die, it is not permissible. Rather, one should say: "O Allah, grant him life if life is better for him, and cause him to die if death is better for him."