There's certainly a history of "guys" being used specifically for men, as in "Guys and Dolls"; however, there is also an (increasing, I think) acceptance of its

There's certainly a history of "guys" being used specifically for men, as in "Guys and Dolls"; however, there is also an (increasing, I think) acceptance of its use in reference to mixed or even all-female groups. But not everyone is equally comfortable with that usage. In many contexts I think it should be clear enough whether an inclusive or gender-specific meaning is intended, but some people may prefer to avoid any risk of misunderstanding by choosing a different word. And unfortunately, as seems all to common these days, some may choose to see offence where none was intended.