Earlier quoted context omitted.
Why do you think that person wasn't an adult?
Because it is very odd framing, to say the least, to refer to someone in a professional context as a "girl."
In this casual retelling I read it as a neutral noun describing gender.
Substitute the equivalent here with 'guy' and we wouldn't be having this discussion.
Thinking harder, I guess 'gal' would have been more appropriate. But in any case I feel this reveals more about the reader and their proclivity to engage in 'culture-war topics' than anything substantial.