bar girl vs adult female

bar girl and adult female both are nouns.

Word	Noun	Adjective	Verb	Adverb
bar girl	Yes	No	No	No
adult female	Yes	No	No	No

As nouns, adult female is a hypernym of bar girl; that is, adult female is a word with a broader meaning than bar girl:

Other hypernyms of bar girl include woman.

bar girl (noun)	adult female (noun)
a woman employed by a bar to act as a companion to men customers	an adult female person (as opposed to a man)