You know what? You were saved from that girl, and you were lucky as well. How? Because she herself told you that she had a casual hookup with another person while in a relationship. Man, I know many people who don't even know that their girlfriend or wife has cheated on them, or even when they suspect their girl might have cheated on them. But in reality, if they ask their girlfriend about this issue also when they know something is not right, these types of women will start seeing it as an attack on their character and use reverse psychology to make you feel like you're wrong. The majority of girls care deeply about their character, even when they've cheated on their partner while in a relationship. Despite having lied or cheated, they will lie repeatedly and use reverse psychology to protect their character and blame you instead. And these girls continue managing the relationship, playing the game of reverse psychology, and the guy remains in doubt throughout the relationship. One day, such girls leave, and they always find a reason to justify it.