From Happy Feminism:
“The question then is: why isn’t it as offensive to call an adult woman a “girl” as it is to call an adult male a “boy.” Is it just because women have accepted a lower position in society or does the term “girl” just not carry the same negativity associated with the term “boy”?
Regardless of which word you use, it’s important to know the impact of your words. Each word categorizes its subject with a fixed meaning, so it is crucial that our words categorizing people maintain equality.”
Why the difference?
Girl 2.(b) sometimes offensive: a female servant
Boy 1. often offensive: a male servant