From Rome with 3 hour stop in GUANGZHOU, onward to Melbourne (Australian Citizen)

Hello, I hope you can clarify. My mum will be travelling from Rome and has a 3 hours stop in GUANGZHOU, and will then fly to her destination in Melbourne, Australia. She is an Australian citizen.

On her way to Rome a few weeks ago, she landed in Shenzhen, China and was reprimanded for not having a visa, even though she was only transiting through and did not intend to leave the airport. She had to complete an application there etc etc.

Can you clarify that she does not need to apply for a visa for her stop in GUANGZHOU? She will not leave the airport. Can she just arrive expecting that she will have the 24 hour visa free transit and so doesn't need to apply for anything before she flies?

The information online is very confusing! Thank you very much.

Kylie