I've never met a girl
Charlie.
Charlotte hasn't been popular in South
Africa, so I suppose the nicknaming process for it never really kicked in. (Where there are Charlottes, in my experience they speak Afrikaans as their first language and pronounce it sharLOT.)
I was at school with a
Charlene, not the famous one, who was known as
Charles for some reason - not a butch lass at all - but never
Charlie. All the Charlies I've known have been guys, and I tend to think of
Prince Charles Edward when I hear it.