Nightclub Girl

In casual context, the word has positive uses, as evidenced by its use in titles of popular music. It has been used playfully for people acting in an energetic fashion (Canadian singer Nelly Furtado's "Promiscuous Girl") or as a way of unifying women of all ages on the basis of their once having been girls (American country singer Martina McBride's "This One's for the Girls"). These positive uses mean gender rather than age.
Demographics
Slightly more boys are born than girls (in the US this ratio is about 105 boys born for every 100 girls), but girls are slightly less likely to die than boys, during childhood, so that the ratio for under 15 years of age is 104 boys for every 100 girls. Since the 18th century the human sex ratio has been observed as about 1,050 boys for every 1,000 girls born and sex selection on the part of parents further lessens the number of female births.