You said she woke up crying, she then confessed to you. That seems like she is genuinely remorseful. Maybe she just wants to know she is still sexy to other men, it may have been a way to reinforce her worth in some twisted way.
Maybe she is like a child, and by telling you she was going out with girlfriends, she was hoping you would say 'No', an effort to know what the boundries are in your relationship.
Do you still love her? Does she still love you? Counseling can help.
Sometimes people just act stupidly, then realize how dumb they were and how they jeopardized what is important in their life, and are truly remorseful.
I hope that whatever you do, you can find peace of mind.
Best regards!