Passport expiring soon

[Andy500]

Hi, I have a question about passport expiration requirements. My wife and I live here in the US. She has her green card, and she has a 6-week roundtrip flight scheduled in a couple weeks to go back to China to visit her mom, and is scheduled to return to the US the second week of June. Her Passport expires in August so we didn't think it would be an issue. A friend of hers told her she might run into a problem on her return flight because China might not let her leave the country if she doesn't have 6 months left before her passport expires. Is that a possibility? Is there anything we can/should do to avoid complications?

Thank you in advance for consideration.