Somewhat of a follow-up to a previous question. I was listening to a podcast recently. The host detailed a conversation with "young girl", who in fact turned out to be 23 years old. My reaction was "she's 23 years old. She's a young woman." I've seen similar posts like that here, where a female user will say something like "I'm a 29-year-old girl" or something or other.
So when does a girl become a woman?