I'm finding with her at least, you don't have to tell her that, she will know it. It's the way other people talk to her, and treat her that is the biggest struggle.
How many times I had to post "I was thinking CEO or POTUS, but you never know" under a facebook photo where some older WOMAN would talk about how beautiful she was and how she'll grow up to be be a model or some other looks based thing.
I tell my daughter she is adorable and beautiful all the time too, but within the context of a result of her and her actions, not as a definitive aspect of her being.
I agree in general. However it's important to note that even "ugly" and "out of shape" people are much more well received when they conform to general fashion guidelines and hygiene protocols.
Looking like you give a shit, and not having offensive body odors etc goes a long way.