Many people don't believe in objective beauty because they don't believe in objective values. An idea is objective when it can be logically traced to reality. For example, our numbering system 1-10 is objective because it is possible in reality to have 1 apple, or 2 apples, or 3 apples etc. Therefore female beauty can also be objective when the things it refers to are real. For example, if a woman is beautiful because she looks or acts brave, her beauty is objective because bravery is an objective value - one that in reality is necessary for an individual human being to survive. Without it in some degree none of us could face a single day. The same is true of health, purpose, happiness, sex, love, wealth, success, etc etc. Women are only beautiful when they represent values, and if the values are objective, then their beauty is too.