Can further entries be added to a multiple entry visa?

Once a visa is issued, the visa can't be changed, it is impossible to add additional entries to a double entry visa. Your friend doesn't need to cancel her visa, once she gets a new China visa, her previous China visa will automatically expire.

There are two methods to solve this problem:
1. She can use her double-entry visa to enter China visa for two times, for third entry to Shanghai from Tokyo, she can apply for a single-entry transit visa or tourist visa in Tokyo.

2. She can use her double entry visa to enter Shanghai once, when she returns to her country, She can apply for a new double entry visa, once she gets it, the previous double entry visa automatically expire. Then she can use the new double entry visa, she can use it to enter Mainland China in December and return to Shanghai from Tokyo.