Is it permissible for a son to make up the missed prayers for his deceased mother who was ill, and will she receive the reward for that?

There are two scenarios for a woman to pray while she has a stroke:

First: If she retains her intellect and discernment, she should pray to the best of her ability. She should purify herself with water or tayammum and pray in whatever manner she is able, even if by gesturing. Prayer is not waived for her.

Second: If she loses her intellect and consciousness, then prayer is waived for her, and she is not required to make it up after she recovers. Similarly, she is not required to make up prayers she missed when she was capable of performing them.