Trying to keep the discussion about language and meaning, and hopefully not getting socio-political, is "girls" a valid counterpart for "guys", as in "guys and girls"? The intention is to describe a mixed group of men and women in suitably casual terms.
"Guys" is unproblematic. However, "girls" could be taken to be diminutive. I personally don't, as I understand the intention to simply be equivelent to "guys", but I can see how some might take issue with it.
It seems that a generation or so ago it was common enough to say "guys and gals", but "gals" seems archaic now.
If not "girls", then what?
Also, it seems that "guys" can be used to mean both men and women, without having to specify the presence of women. However, I think the default assumption is still an all male group. In any case, I'm looking for an uncontroversial casual term for a group of women on the same level as "guys".