Is the death of the grandmother after the mother's departure and her asking for forgiveness without a response considered an act of disobedience on the mother's part?

What the mother did by going out with her husband to where he commanded her is her duty, because the husband has more authority over his wife than her parents, and obedience to him is more obligatory upon her. Therefore, there is no sin upon her, and no reason for the mother to cry or despair. Rather, she should pray for her mother for forgiveness and mercy. A parent's prayer for their child is answered, and this includes both parents. If a child is dutiful to their parents, forgiveness and high status with Allah Almighty are hoped for them. If a slip occurs from them, it is a cause for forgiveness, as Allah Almighty says: "Your Lord is most knowing of what is within yourselves. If you should be righteous, then indeed He is ever Forgiving to the often returning [to Him]."