Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.

To proceed:

The principle on making up and adorning oneself is that it is permissible. To this end Allah the Exalted says: “Say (O Muhammad): “Who has forbidden the adoration with clothes given by Allah, which He has produced for his slaves, and At-Taiyibat [all kinds of Halal (lawful) things] of food?” [al-A’raf: 32]. Another evidence to this is a hadith transmitted by Muslim on the authority of ‘Abdullah IbnMas’ud who said that the Messenger of Allah (peace be on him) said: “Allah is beautiful and He loves beauty.” This shows that beauty is loved by Allah the Exalted. This includes beautiful clothing because when the Messenger of Allah (peace be on him) was asked by a someone: What about that a person likes fine dress and fine shoes? He replied: “Allah is Beautiful and likes beauty.” In al-Fawaid (page 184), Ibn al-Qayyim (may Allah have mercy on him) said: “The beauty (mentioned in the hadith) generally includes every type off beauty.” There is no doubt that inner beauty comes before any other type of beauty such as beauty of structure and appearance. After mentioning the favour of clothing that He gave mankind to cover his awrah and beautify his appearance, Allah the Exalted says: “But the garment of righteousness (restraint from evil), that is the best.” [al-A’raf: 26]. What is being meant is that looking beautiful is permissible for men and women except that the need for beauty is more on women. Regarding this Allah the Exalted says: “(Do they Then like for Allah) a creature who is brought up In adornments (wearing silk and gold ornaments, i.e. women), and In dispute cannot make herself clear?” [al-Zukhruf: 18]. Therefore, Allah permitted women to adorn themselves with gold, silk and other jewellery more than He did on men.
With regards to your question on working in a beauty parlour and getting a salary for that; it is permissible based on the general principle derived from the verse: “whereas Allah has permitted trading and forbidden Riba (usury).” [al-Baqarah: 275]. This is also the view held by majority of scholars but Imam Ahmad (may Allah have mercy on him) detested the earnings of a hairdresser. Al-Hasan transmitted that some scholars forbade putting makeup because mostly it is not devoid of prohibitions or changing the creation of Allah. What is apparent to me is that it is permissible as long as it does not involve taking a salary for impermissible makeup such as plucking of eyebrows and the like, which was prohibited by Allah and His Messenger (peace be on him).
However, with regards to the issue that a woman might attend unlawful gatherings with this adornment; the issue is not devoid of three cases:
First: Knowing that the adornment is meant for what is prohibited. In this case it is not permissible to do her makeup and whatever money she gets from that is unlawful.
Second: Knowing that the adornment is meant for what is lawful. In this case it is permissible to do her makeup and whatever money she gets from that is lawful.
Third: Not knowing if the adornment is meant for what is prohibited but having a strong suspicion on that. In this case it is not permissible to do her makeup, however if there is no strong suspicion then it is permissible to do her makeup.
And Allah knows best.

Your brother,

Dr. Khalid al-Mosleh