Oh no she owned up to it eventually...she apologized and told me she was stupid for saying that stuff. That was the "insert bullshit" in my message.

It doesn't really matter if she cheated on you or not. The question is, will you be able to trust her? You have a few options in your situation right now.

1. You can stay with her and know you can trust her.
2. You can stay with her but you will have trouble trusting and end up having problems later on and probably breaking up.
3. You can leave her because you know you won't be able to trust her.

It's all up to you right now, we can't tell you what to do.