adult female vs grownup

adult female and grownup both are nouns.

Word	Noun	Adjective	Verb	Adverb
adult female	Yes	No	No	No
grownup	Yes	Yes	No	No

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

Other hypernyms of adult female include adult, female, female person.

adult female (noun)	grownup (noun)
an adult female person (as opposed to a man)	a fully developed person from maturity onward

adult female (adjective)	grownup (adjective)
	(of animals) fully developed