mother superior vs adult female

mother superior and adult female both are nouns.

Word	Noun	Adjective	Verb	Adverb
mother superior	Yes	No	No	No
adult female	Yes	No	No	No

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

Other hypernyms of mother superior include superior, woman.

mother superior (noun)	adult female (noun)
the superior of a group of nuns	an adult female person (as opposed to a man)