The meaning of the French word Beau is to be good looking, handsome, gorgeous etc.
Being called a Beau whether male or female is a good thing.
My Grandma used to call me a Beau when I would visit her as a kid and I never really knew what she meant but later I asked her and she said it meant I was a handsome little boy and a gorgeous good looking boy.
The word beau means fashionable, beautiful, gorgeous, handsome or really likable or lovable.
A female beau is a female who is gorgeous, beautiful and very lovely.
So if a man refers to you as a female beau then the man is complimenting you and saying you're are very gorgeous, likable, lovely and beautiful.
A male beau is a handsome, lovely, good looking male and a female who says that to a male is also complimenting the male.
Being called a beau is a good thing.
The word beau is a very old word and saying and is just a nice way of saying someone is very lovely.