What is the ruling on a wife going to a women's beauty salon, and is it prohibited due to what it may involve of supporting evil deeds, or the presence of forbidden things such as plucking eyebrows and looking at 'awrah (parts of the body that should be covered), or secretly taking pictures?

If the discussion is about what is primary and preferable, then there is no doubt that it is acceptable. As for the boundary between lawful and unlawful, the ruling on the prohibition of going to beauty salons depends on the presence or absence of Sharia-related caveats, such as the forbidden plucking (namṣ) or the exposure of 'awrah (private parts). If the woman adheres to the Sharia guidelines and no caveats are involved, then it is not ruled as forbidden. Sheikh Ibn Uthaymeen issued a fatwa permitting going if the beautification is permissible and not forbidden, such as plucking the face, which is considered one of the major sins. Dar Al-Ifta Al-Masriyyah (the Egyptian Fatwa Council) permitted a woman to beautify another woman provided that it is away from the eyes of strangers and that the beautification is not for strangers or for what is not permissible for her. As for the issue of the possibility of taking pictures, it is not considered unless the possibility is strong and supported by evidence.