Rule of thumb: A woman should want to look good for you and that means she pays for her own beauty products. Always pay for her beauty products if she's getting dolled up for you.
For example, if you invited her to a wedding you should pay for her hair, nails, clothes, etc. If you're with her and she gets some beauty products you should pay for them. She's getting sexy for you. You're not tricking you're investing in your relationship. Buy her expensive shyt that lasts months like perfume, lotion, make up, purses, shoes etc. Hair and nails need monthly maintenance and that gets expensive.