If he cheated with you will he cheat on you?

Me and my wife were having a discussion lst night about a friend of hers. She said this girl called her all upset about her husband. Apprently when they met some years ago he was dating someone else and she knew it. She would go over to his house and hang out and after a few months that turned physical. He eventually left his girl for my wife's friend. He also told her he has a ton of female friends, some of which he's dated before and my wife's friend went along for the ride. During their relationship they both strayed a bit but they got married. Now she is upset that he still has eyes for other women. She feels that now that he's married to her he should not want to look at any other women or even try to hook up with them. Now this is the very same girl who cheated with him when she knew he was involved with another girl but didn't care. Now she wants / expects him to remain faithful now that they are married. He wasn't faithful to her when they first met, started dating or even got married but she can't understand that if he cheated with you he'll cheat on you. Is she wrong to expect her husband to be 100% faithful? That sounded silly as I typed it so let me say this. She knew he was that way when she met him but did she think she would be the one to change him?