Been with this girl about 3 months. She got out of a long relationship with a very bad breakup where he left her, and we met about a month and a half after that ended. Things have been great for the past 3 months, and I never once suspected that something was up. However, last week we were driving in my car, and I looked over and saw that she received an email from him saying "You coming over tonight?". She was devastated after her breakup and really loved this fuck, she promises they have never seen or talked to each other at all since we started dating, but I find it so strange what the email said. She showed me she had him blocked everywhere but says she never even considered emails. She was crying a lot says she would never do something to jeopardize our relationship. She's spent a ton of time with me since this happened, and I'm positive nothing happened between them. What do I do exactly? Bail, or just lay down the law that I'll walk away if something's going on. I quickly brushed it off because it seemed so sincere, and she was so upset, but my gut tells me something is up.

Update*

They were definitely fucking. Someone said I should have asked her to respond to him in front of me so I did this:

"message him back and say why did you ask that the other day". She refused and put up a huge fight. I asked to see her emails and she went fine! Nothing in the inbox from him / nothing in the sent file from either of them. Then checked out the deleted and found nothing. Phewf. But then I realized there wasn't even the email he sent in her deleted folder. Went to restore deleted messages (hotmail) and literally hundreds of emails between the two of them. The last one was terrapin12345 saw your message. I can't see you anymore it's not fair to terrapin12345 - but I don't regret anything between the two of us. WTF