What do you think of Bethany walking in and telling him that it was my fault that she was there?
Are you going to get back at her?
I'm going to expose my cheating girlfriend as a slut
It is not good that she blamed you for something you didn't do and you should feel upset about it but you should be careful about getting back at her. It would be better to clear the air with him instead.
I'm going to expose her as a slut anyway.
Although you are hurt, spreading rumors about someone is wrong. It would be best to express how you feel directly to the person and then move on.