i am a travel agent and my client is currently in China and had her passport stolen that, also has her Chinese Visa. does she require a Visa to depart China?

Your client needs to report to the lost of passport to the local police station and get a Lost Report, then go to the nearest embassy/consulate of his country in China to apply for passport or emergency travel document, then go to the Exit-Entry Administrative Department to apply for a valid China visa, then depart China.

If your client has the copy of his passport and China visa on his passport, this problem will be easily solved.