I think it's situational. Most groups of women refer to themselves as 'girls' in social situations. We Southerners use lady rather interchangably.

Several years ago a group of us girls were on the gulf and took a morning fishing trip. The captain referred to us as girls and then quickly back-pedaled, not wishing to offend. I laughed and told him we were old enough to appreciate being called girls since we really weren't anymore.