You're reading too much in to it. This was the informal title the curators often used for the painting. It was a sign of affection for what is a wonderful painting of a very enigmatic young woman. The art historians and scientists we worked with always used the formal names of course.
Even better, the young woman in the painting isn't a girl and she isn't even real. It's all imagined by Vermeer.
No one minds that she is called a 'girl' when she is most definitely a young woman even by today's standards and most definitely by the standards of the day.
All of this was 20 odd years ago though, for me, when the term chick was much more widely used in both the US and UK.
> the young woman in the painting... isn't even real
There is some evidence that Vermeer could have been using optical tools to create his photo-realistic paintings.
If so, she would have been a real person, as that is how the technique is imagined to work - use an optical apparatus that allows you to see your painting and the subject in the same view, and then paint so that they blend into each other.
A pretty cool documentary was made about this called Tim's Vermeer[1] (starring Tim Jenison and directed by Penn & Teller), and led to an installation at the Museum of Old and New Art (MONA) in Hobart, Tasmania. Really interesting, and well worth experiencing both!
