Question Detail: I married Chinese wife in May 2013 in China. Wife entered the US on November 2014. I-751 was due November 2016 but I did not complete i751. I want to help her but she is totally unpredictable. She wants to travel to Mexico. If she goes there, can she reenter the US?
Answer: if your wife and you failed to file I-751, application to remove condition, her green card expires and she may have problem coming back. She may also be placed in removal proceedings if she is lucky.
You should file a late I-751 immediately.