It depends on the context and who is using the term. "Mate" can be used to refer to women, but it has nuances.
According to the reference material, here's a breakdown:
- Generally acceptable among female friends: It's not unusual for a woman to talk about her "mates" or refer to another woman as one of her "mates," indicating friendship.
- Masculine usage: There's a more masculine way to use the term "mate."
- Less common: You wouldn't typically hear a bartender addressing a woman with "what can I get you, mate?"
- More common: It's perfectly normal to say that to a man.
Therefore, while not universally applicable, calling girls "mate" can be appropriate, especially in the context of female friendship. The appropriateness depends on the situation, tone, and relationship between the speakers.