What is meant by "whom Satan confounds by touch"? Can a praying person be bewitched? What is the ruling on accompanying one's mother to a raqi when she is convinced she is bewitched?

The one described as being "overcome by Satan" is the insane, epileptic person, and "possession" refers to madness. A person praying can be afflicted by magic, as the Prophet, peace and blessings be upon him, was afflicted by magic. There is no harm in accompanying your mother to the Raqi (exorcist) if you are certain that he performs Ruqyah according to Islamic law, while adhering to Islamic manners, such as not being in seclusion with her or revealing any part of her awrah to him.