girl vs female offspring

girl and female offspring both are nouns.

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

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

girl (noun)	female offspring (noun)
a young female	a child who is female
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