councilwoman vs adult female

councilwoman and adult female both are nouns.

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

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

Other hypernyms of councilwoman include council member, councillor, woman.

councilwoman (noun)	adult female (noun)
a woman who is a council member	an adult female person (as opposed to a man)