Are the problems that the questioner and her sister are experiencing due to their ill-treatment of their grandmother? Will Allah forgive them for that? What should they do to expiate their sin? And how should they deal with their mother, towards whom they feel the same emotions that their mother had towards their grandmother?

You must honor your mother and be good to her, and you must repent for having wronged her, for the mother's right is immense, and disobedience to her is a grave sin. You must also repent for having wronged your grandmother, for she has a great right, similar to that of a parent. When you feel a lack of success, you must review yourself and renew your repentance, for sins and acts of disobedience are the cause of affliction. Allah the Almighty said: "O My servants, it is only your deeds that I record for you, and then I will recompense you for them. So, whoever finds good, let him praise Allah, and whoever finds otherwise, let him blame no one but himself." Sins remove blessings and bring about misfortunes. Hasten to general repentance and strive in righteous deeds, and among the greatest of these is honoring your mother, for it is one of the best deeds for expiating evil deeds.