Wikipedia's article on Geisha states:
"Geisha girls" were Japanese women who worked as prostitutes during the period of the Allied Occupation of Japan. They almost exclusively serviced American GIs stationed in the country, who referred to them as "Geesha girls" (a mispronunciation).
These women dressed in kimono and imitated the look of geisha. Americans unfamiliar with the Japanese culture could not tell the difference between legitimate geisha and these costumed prostitutes. Shortly after their arrival in 1945, occupying American GIs are said to have congregated on the Ginza and shouted in unison, "We want geesha girls!"
Eventually, the term "geisha girl" became a general word for any female Japanese prostitute or worker in the mizu shobai and included bar hostesses and streetwalkers.
Geisha girls are speculated by researchers to be largely responsible for the continuing misconception in the West that all geisha are engaged in prostitution.
This would suggest that "geisha girl" isn't used for actual geisha.
However, Google ngram suggests that the term was used about as much before World War II as after it, which seems inconsistent with Wikipedia's description of how the term became popular.
Choosing one example of a novel written before World War II (The Ragged Edge, by Harold MacGrath), where the term was used for actual geisha:
The manager twisted his moustache. "The same as a Japanese geisha girl."
"And what is a geisha girl?"
"The geisha and the sing-song girl are professional entertainers. They are not bad girls, but the average tourist has that misconception of them. If some of them are bad in the sense you mean, it is because there are bad folks in all walks of life. They sell only their talents, not their bodies; they are not girls of the street."
In addition, the definition of geisha girl given by several of the dictionaries linked to by onelook.com suggest that "geisha girl" is a synonym for actual geisha:
a Japanese woman trained to entertain men with conversation and singing and dancing
Is "geisha girl" used to refer to actual geisha? And has the term been used to refer to women who aren't actually geisha, such as prostitutes for American GIs, or bar hostesses?
Background: I came across a tourism brochure, written in Japan and presumably by Japanese people, which captioned a geisha as a Geisha girl in a Chaya area, and I wanted to know if they made a bit of a blunder.