US citizen VOA?

Hi,

My friend just waited over 3 hours at the China Visa Services in Hong Kong for a single entry to visit Shenzhen for one day. When she was finally called up they rejected her application (since she is not a HK resident) and indicated she should get the VOA at the border. I don't want to take her all the way to the border for another potential rejection so any advice indicating this is the correct course of action is most appreciated.

Thanks for your time.