Is it permissible to perform ruqyah on a friend's sister and treat her for sihr with ruqyah shar'iyyah?

It is permissible for a Muslim man to perform ruqyah on a non-mahram woman, provided he adheres to the Sharia guidelines, such as avoiding seclusion (khalwa) and refraining from touching or looking at the non-mahram woman except out of necessity. Evidence for this permissibility includes the hadith narrated by Ibn Abbas in the Sahihayn concerning a woman who used to have epileptic fits and would become uncovered, and the hadith in Sahih Muslim: "Whoever among you can benefit his brother, let him do so."