Based on my undersatnding, your child has to get the immigration visa and enter US, then she can file N-600 to get the US citizenship, so I still feel weird that NVC said that your child can apply for the US citizenship certificate at the same time with the immigration visa application outside US. So, you may consult an immigration lawyer or talk to NVC to make sure they did not make a mistake. I have not found an immigration law to support the NVC suggestion.