What is to be done about the recurrence of words associating partners with the Oneness of Allah, despite adherence to prayer, fasting, and Qur’an recitation, and the ineffectiveness of the grandmother’s Qur’an recitation?

"Waswas" (obsessive whispering) is an illness that can be treated, for Allah has not sent down a disease without sending down a cure for it. For its treatment, you can refer to fatwas numbered: 31097, 31098, 32483, 31469, 31611. You can also seek psychological consultation from the website.