I think it depends on the rules of the place that you're taking her to. Where I am there is 1 piercing studio that will do them at 3 months, but that's the earliest I've seen.
It varies depending on the place. Try her pediatrician first; placing like piercing pagoda use nail guns that are more difficult to clean and can lead to a greater chance of infection. Many pediatricians now offer ear piercing and it is done at the office with a new and sterile needle. Much more hygienic!
Re: Baby girl - ear piercing