Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Basically working in a saloon is permissible as long as the person does not commit any prohibition such as plucking eyebrows, attaching artificial hair, or seeing Awrah (parts of the body that should not be seen), etc. No doubt, full-body waxing necessarily means looking at Awrah which is forbidden in Shariah. Also removing hair from eyebrows is forbidden. The Prophet (Sallallahu Alaihi wa Sallam) said: "Allah curses those ladies who practice tattooing and those who get themselves tattooed, and those ladies who remove the hair from their faces and those who get their hair removed from their faces and those who make hair pieces and attache them to other women’s hair and the women who have their hair lengthened by artificial hair."
He also said: "Any woman who puts off her clothes in other than her husband’s house, has torn off the screen which is between herself and Allah." [Ahmad, the Hadith is correct]
Therefore, we advise this sister to limit her duties only to that which is lawful and not remove hair from eyebrows, attach hair to hair or see the Awrah.
Allah knows best.