girl vs female person

girl and female person both are nouns.

Word	Noun	Adjective	Verb	Adverb
girl	Yes	No	No	No
female person	Yes	No	No	No

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

Other hypernyms of girl include female.

girl (noun)	female person (noun)
a young female	a person who belongs to the sex that can have babies
a girl or young woman with whom a man is romantically involved
a youthful female person
a friendly informal reference to a grown woman
a female human offspring