nymph vs adult female

nymph and adult female both are nouns.

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

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

Other hypernyms of nymph include woman.

nymph (noun)	adult female (noun)
a larva of an insect with incomplete metamorphosis (as the dragonfly or mayfly)	an adult female person (as opposed to a man)
(classical mythology) a minor nature goddess usually depicted as a beautiful maiden
a voluptuously beautiful young woman