"What about what is appropriate in a 'professional' work place?"
Do you mean, is "gal" appropriate in the workplace? I think you could get away with it in most workplaces. Maybe not the super-formal ones.
In a formal workplace, "men" and "women" will tend to the proper terms. "Gentlemen" and "ladies" for the really fancy places.
I don't think society's rules about what is or isn't the appropriate word/s for men and women are very cemented yet. There's some squishiness going on. I mostly try to just think of what words "feel" the most appropriate for the situation at hand.
And promptly prepare to apologize as necessary.