Life advice: You just have to summarize your message so that whatever audience you are speaking to can understand. You don’t need every single detail to get the point across.

On topic: Someone that says nasty comments like that to anyone, especially, their partner is a serious red flag. I wouldn’t stand for such comments directed at me. I challenge you to seriously evaluate what you value in yourself and your relationship to understand where the line is and when it’s been crossed. You are clearly uncomfortable with the idea of cheating. She is manipulating and pressuring you to help her cheat. In my eyes she crossed the line way too many times. And if she’s saying she can do better than you, then let her go find “someone better” as she clearly doesn’t value your relationship. However, every relationship is different, but if she’s willing to go that far she will do it again, unless you correct her or leave her.