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Then, she does not need to contact the US Consulater. She needs to file I-824 to USCIS for her spouse to apply for the immigrant visa in China following the I-824 Instructions.

See:

Application for Action on an Approved Application or Petition | USCIS

Select Item "1.c." of Part 2 in Page 2 of I-824, and fill "US Consulate in Guangzhou" in the blank in this item. Consult an immigrant lawyer if necessary.