Answer
Dreams are not in our control or in the control of the deceased. It is the Will of Allah.
No deceased comes in one’s dream by his/her own wish. There is no reason for you to feel grief for not seeing your mother in your dream. You should perform acts of virtue, for example, recite the Qur’aan, perform Nafl Salaat, offer charity and make the intention of giving the reward to your mother. Be rest assured that she is receiving your reward and loves you very much.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai