I've always liked to give people the benefit of the doubt.. If she trully does not want to be a cheater, she won't be.
Unfortuntely, this has also taught me some valuable lessons. Now, I do believe once a cheater, always a cheater. After you've done it once, it's easy to do it again.
Personally, the red stop signs are showing up everywhere based on her past experiences. You're only as good as the choices to made to become the person you are today. There is no such thing as "forgetting the past". You made those choices, you decided to be the person you are, now deal with it. If you have a problem with it, you should've have done what you did. Plain and simple. Self-respect isn't what it used to be...