mestiza vs adult female

mestiza and adult female both are nouns.

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

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

mestiza: a woman of mixed racial ancestry (especially mixed European and Native American ancestry)
adult female: an adult female person (as opposed to a man)

Other hypernyms of mestiza include woman.

mestiza (noun)	adult female (noun)
a woman of mixed racial ancestry (especially mixed European and Native American ancestry)	an adult female person (as opposed to a man)