Help recovering from fiance's Emotional/Physical Affair?

I was afraid my girlfriend/fiance would leave me after she had an affair with a . Upon further study of the situation, it was both a physical and emotional affair, with all of the trappings of both. It was a rough go of it, but we've finally reached a place where we're moving on. However, I still struggle sometimes with feelings of betrayal and distrust. I have to actively fight against the urge to pry into her privacy (reading emails, monitoring her online activity, reading her phone messages, her diary, etc.) She has ured me that the affair is over, and for the most part I believe her. However, she emerged from the affair a changed person and seems to not want to devote as much free time as possible on our relationship, choosing instead to be out with her new friends she's made. She has accused me of being selfish, and attempting to hold her prisoner in the house so I can keep an eye on her. Am I overreacting? Or should I give it more time?