Absolutely if you work on a unisex Salon you should treat both sexes.
The salon may be unisex, but why should that require all people working there to be unisex?
I can see conflict if the salon had that view and an employee didn't, and the law would need to take a position there.
But if the salon and employee are in agreement that an employee does female-only, are you saying the law should say "no, sorry, you aren't allowed to have female-only staff, you have to make all staff do both sexes". Really?