Worrying that you're going to lose someone is often the fastest way to ensure that happens.

Why? Because your girlfriend will most likely, at some point, pick up on your insecurity, however subtle it may be. There is nothing more likely to end a relationship than feeling pressured by an insecure partner. Good healthy relationships exist when couples are completely confident and at ease with eachother and don't place demands on them. You say you trust her, yet you are clearly worried enough to post here.

Her past is her past, as others have said. She is with you now. It would be sad if both your reading of her emails and your susequent worries over her past drives her away.

Me and my ex didn't have the best of relationships (he was very possessive) but one thing I did appreciate was when he told me he found a friend of ours attractive. He would NEVER have acted upon it and assured me so, but I found his honesty very refreshing. Allowing someone space to be who they are is very lovable. Obviously there are boundaries - but finding people attractive is a fact of life, in relationship or else.

I feel that you perhaps need to look at what drove you to read your girlfriend's emails and consider what is in the past and what is now. The more suspicious you become the more a wedge is being driven between you.