freewoman vs adult female

freewoman and adult female both are nouns.

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

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

Other hypernyms of freewoman include freeperson, woman.

freewoman (noun)	adult female (noun)
a female person who is not a serf or a slave	an adult female person (as opposed to a man)