My sister who is born in the US holds a US passport however, both of my parents have a Chinese passp

My sister who is born in the US holds a US passport however, both of my parents have a Chinese passport. She is currently staying with me in the US and wants to return to China to visit friends and my parents in China this summer. So she needs to apply for the travel document? If so, what documents does she need to provide for the consulate? I tried calling the Consulate but no one ever picks up the phone.