valley girl vs missy

valley girl and missy both are nouns.

Word	Noun	Adjective	Verb	Adverb
valley girl	Yes	No	No	No
missy	Yes	No	No	No

As nouns, missy is a hypernym of valley girl; that is, missy is a word with a broader meaning than valley girl:

valley girl: a girl who grew up in the tract housing in the San Fernando Valley
missy: a young female

Other hypernyms of valley girl include fille, girl, miss, young lady, young woman.

valley girl (noun)	missy (noun)
a girl who grew up in the tract housing in the San Fernando Valley	a young female