salesgirl vs sales rep

salesgirl and sales rep both are nouns.

Word	Noun	Adjective	Verb	Adverb
salesgirl	Yes	No	No	No
sales rep	Yes	No	No	No

As nouns, sales rep is a hypernym of salesgirl; that is, sales rep is a word with a broader meaning than salesgirl:

salesgirl: a woman salesperson
sales rep: a person employed to represent a business and to sell its merchandise (as to customers in a store or to customers who are visited)

Other hypernyms of salesgirl include sales representative, salesperson, adult female, woman.

salesgirl (noun)	sales rep (noun)
a woman salesperson	a person employed to represent a business and to sell its merchandise (as to customers in a store or to customers who are visited)