The phrase "birthday girl" refers to a female who is celebrating her birthday. It is a common term used to describe the honoree at a birthday party or gathering.
The little birthday girl looked darling in her homemade paper party hat. (mommyscene.com)
And so here we have this delicious pink mousse, which not only is a delicious stand alone treat, but makes the perfect mousse frosting to satisfy little birthday girls and their friends. (twospoons.ca)
It sounded good at first: Gift recipients, such as young birthday girls, could post their wish lists for others to see. (entrepreneur.com)