working girl vs hooker

working girl and hooker both are nouns.

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

As nouns, hooker is a hyponym of working girl; that is, hooker is a word with a more specific, narrower meaning than working girl:

working girl (noun)	hooker (noun)
a young woman who is employed	a prostitute who attracts customers by walking the streets
a woman who engages in sexual intercourse for money	(rugby) the player in the middle of the front row of the scrum who tries to capture the ball with the foot
	a golfer whose shots typically curve left (for right-handed golfers)