It implies that your friend lives in Hong Kong or Taiwan, and that China employs people to read Facebook posts from those places. Unless you mean that she sent you a messenger chat (which now has end-to-end encryption). In that case, she lives in Hong Kong or Taiwan and the Facebook encryption should not be relied on to protect yourself from Chinese monitoring.
Using a VPN because it's blocked.
That's right. And will she be detained for using Facebook or VPN?