Is it possible to pray with the intention of compensating for the shortcomings of a deceased mother in her prayers? If that is not permissible, then how can one honor her in this specific aspect? Does the recitation of the Qur’an and seeking forgiveness reach the deceased? What are the deeds that can be done to honor her after her death?

If the deceased mother committed to prayer, fasting, and obedience in the last part of her life, this is an indication of her good ending; for what matters is the ending, as stated in the hadith (definition) of Ibn Mas'ud. The mercy of Allah is more hopeful than any deed, and His forgiveness is wider than all sins. It is not prescribed to make up the prayers on her behalf, but you should supplicate for her, give charity on her behalf, and seek forgiveness for her. The preponderant opinion is that the deceased benefits from the reward of reciting the Quran and from dedicating the reward of any act of obedience to them.