Is the sudden death of a daughter due to seeing her mother die before her eyes considered a sign of impatience, discontent, and lack of perseverance?

It cannot be definitively said that the cause of the girl's death was her grief, discontent, and impatience over the loss of her mother. There is no need to delve into her punishment. One should instead pray for mercy upon her, seek forgiveness for her, and think well of her.