working girl vs woman

working girl and woman both are nouns.

Word	Noun	Adjective	Verb	Adverb
working girl	Yes	No	No	No
woman	Yes	No	No	No

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

Other hypernyms of working girl include adult female.

working girl (noun)	woman (noun)
a young woman who is employed	women as a class
a woman who engages in sexual intercourse for money	an adult female person (as opposed to a man)
	a female person who plays a significant role (wife or mistress or girlfriend) in the life of a particular man