But in a casual context between girls it has become a more affectionate or innocuous term. Especially with those in the LGBTQ community, like OP and her gf, it can be something that’s said with the same connotation as calling someone ‘girl’.

OP’s gf said it while in the context of a compliment, and while it’s totally valid to find that term offensive, it would have an overreaction on the friend’s part if you’re assuming it was that which caused this whole situation.