You might want to consider that you live in a bubble - and that your finger wagging is condescending.
'Girl' is the feminine of 'Guy' - just as much as it is also the feminine of 'Boy'.
Consider those words for a moment and their common usage.
I'll bet that 'girl' is your vernacular as much as it is mine, because it's universally common.
"That guy/girl is smart" - both acceptable.
"The guys/girls are going out for lunch" - both acceptable.
"Guys/girls, huddle in, let's chat" - both acceptable.
"The guys/girls from marketing are in town this week" - both acceptable.