I think that maybe she's talking about mastodon.social but yes, it's not accessible from China. The test shows so:
CHINA ACCESSIBILITY CHECK
Site URL
https://mastodon.social
:
❌ is NOT accessible in Shanghai, China (23.4 million people)
❌ is NOT accessible in Beijing, China (18.8 million people)
❌ is NOT accessible in Shenzhen, China (12.7 million people)
❌ is NOT accessible in Guangzhou, China (11.6 million people)
❌ is NOT accessible in Chengdu, China (10.2 million people)
❌ is NOT accessible in Chongqing, China (8.5 million people)
❌ is NOT accessible in Tianjin, China (12.8 million people)
(Credit:
https://www.chinafirewalltest.co.)