hooker vs working girl

hooker and working girl both are nouns.

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

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

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