What is the ruling on the children of a paralyzed grandmother helping their granddaughter with ablution, and must she perform istinjāʾ for every prayer, taking into account her health conditions?

Prayer is obligatory upon the grandmother as long as her mind is sound. It is not obligatory for you or her children to help her with purification and prayer, but if you do, it is good. If she has money, she must hire someone to assist her.

She must guard her purity and perform istinja' for prayer unless she has urinary incontinence. She is permitted to combine prayers due to her illness. She must pray according to her condition and ability, and whatever she is unable to do regarding the conditions and pillars of prayer is waived for her.

You must teach her and explain what is obligatory upon her in a way she can understand.