Either way, you're still lying. She didn't cheat, she got sexually assaulted by the guy, and never did anything with him. If you're dating a girl, and some guy kisses her against her will, are you going to accuse her cheating, even when you find out it wasn't her fault and she didn't do anything? No. You're not. Well, maybe you will, but that would be extremely unfair to the girl.
That's what happened to Rachel. Some guy kissed her against her will. If that's your definition of cheating, then I can't help you. But if you're going to "warn" people about the game, you should be clear about it. Say, "some guy kisses the MC's girlfriend against her will, but she never did anything else with him". That will send a clear message for people to interpret how they want, instead of saying she cheated on him, which will lead people to believe she had sex with another guy.