I had a similar experience chatting to my former coworker (who moved recently from China) regarding Taiwan. I said Taiwan is pretty much an independent country given it has it's own currency, military and democratic government. She looked at me like I was telling her the earth was flat. She was smart and good natured, and didn't have any opposing reasons, but she insisted Taiwan was simply another province of China.…
As far as she was concerned, Tibetans were Chinese, not a distinct group.
It was eye opening.