Isn't a group of women 'my/some friends', or colleagues, just as a group of men is, for men? I suppose 'mates' is usually male friends, its use by women is probably regional, as is 'lads' night out' as equivalent to 'girls' night out' - both implying youthful abandon.
I'd just say 'some friends' but if pushed to specify would use women friends, if they all happened to be women, or, if it's deliberately an exclusively female group, 'female friends'.
I do accept that in established useage, a girl is not just a child, the word is used for 'young adult' up to about 25 and lad and, increasingly, boy, is used in the same way (something about the extension of youth into 'adult' years).
Girl definitely impies 'young', 'junior' and 'subordinate' though, which is why 'the girl in charge of that department' sounds so very odd and 'give my girl a call' implies he identifies her as a subordinate person, not as a person on an early step in a career.