I prefer
Charlie for a boy, but it's cute for a girl, too. I knew a little girl named Charlee, and that was her full fn (not sure of her mn). I also like
Charlotte,
Caroline, and maybe even Charlize, and Charlie/Charli/Charlee as the nn. But if it's short for
Charlotte, which I love, people might assume it's pronounced like SHAR-lee. Do you like
Carly? That is a cute nn for
Charlotte or
Caroline as well.
:)