L Visa denied

my wife was born in Hong Kong. She is a US citizen with a US passport. She went to the Chinese Consulate in San Francisco to get an L Visa. It was denied. They claim she need sot provide her Hong Kong Birth Certificate which she does not have since she surrendered it at age 10. She has all of the other necessary paperwork. Can someone point me to a website documenting she needs this birth certifiacate from Hong Kong? second, why does she need to have this birth certificate when she has a US passport and proof of citizenship? Why doe sshe not have the same rights as me?