I've thought about what would happen if my girl cheated on me. I'd be furious.
But I might actually forgive her.. I'm crazy about my girl. And if you are too about yours then you should forgive her, just let her know that you need time
Sometimes people do shitty things they never would have done if they were thinking straight. I know this from experience. But does she seem like that kind of person to cheat on you? if she does leave, if not give it time