Travelling back home to China with expired visa?

The question here isn t if going back to China on an expired visa is a problem, but transferring through airports in other countries.

Here s the full story. My girlfriend was an international student here in the USA , she graduated last December with a Bachelors and shortly after applied for OPT, which allowed her to extend her stay. Now, how long she can stay with an OPT all depends on finding a job or not. If she found a job, she could have stayed for another year, but if not, she would have to leave within a couple of months. She was unable to find a job for obvious reasons and was told that she had to leave by mid-June.

The thing is now, her visa expired last December and with COVID, finding a ticket to go back to China directly from the USA is near impossible right now with COVID-19. The easiest solution is to fly to other countries with multiple stops and then flying to China. She found that she can fly from the US to Paris, then transfer flights to Athens, Greece and then fly to China, the flight from Greece to China is even through a different agency, which is a whole other mess of its own. Once she enters the countries, she has to go through customs and that s where our concerns come in. Can she go through customs without any problems with an expired Visa? Her Chinese Password is valid, but we re wondering if that s enough or if that would cause an issue of some sort.