I (Chinese) just went on a couple dates with a white girl and we seem to hit it off but this is actually a concern I have.
She's not Zionist, pro-LGBT and has kind of shaken off the conservative Christian upbringing but being in Australia and surrounded by Australian media, and has concerns about China.
If she's dating you and seems to have an open mind then there's hope. My wife was convinced by media in her country that she'd get hate crimed the minute she stepped off the plane in China. We went for a week and she had a wonderful time and keeps talking about wanting to visit again.
Sometimes the best way to disprove a lie is first hand exposure to the truth.
I wouldn't worry about it. I would talk to her about it and at least show very basic things about China. (High speed rail, big buildings, people generally being happy). If she's a normal human being her opinions will change overtime.
You're worrying about the wrong thing. People like OP don't exist in real life. If they thought the genocide was real they're dumb enough to fall for 100 other blood libels and wouldn't have dated you in the first place. What you need to worry about are women who think the genocide is real and agree with it.