From Longman Dictionary of Contemporary Englishmy girlmy girlold-fashionedCHILDWOMAN used by an older person when speaking to a girl or woman who is younger than they are, or when they are annoyed Listen to me, my girl! → girl
Examples from the Corpus
my girl• This won't do, my girl.• Not really your fault, my girl.• Don't you take him home, my girl.• But the little game's over, my girl.• That's put you in your place, my girl.• It's not what you think, my girl, it's what the man thinks. 