I have been the exgirlfriend and I know how hard it is to stay away from someone you trusted and felt you loved. You feel so sad and yet you feel anger that they have left you.
I found that I had to let go of the anger and that I also had to let go of the person, they did not choose to stay with me and I could not control that. All the phone calls or letters just made me feel worse and the other person think of me as pathetic. So in the end, I did move on as I finally realized he was not hurting me, I was causing my own pain by hanging on to a dream that was gone.
Be happy in your self and your own life and concentrate on the things you enjoy away from the ex. Avoid being around her and perhaps it is time to lose her email.
IMHO I feel perhaps it would be better for you to pull away now and call it a day with her. Show that you have true value, you are better than this, tell yourself that, walk away, don't run after her because that my new friend will push her further and further away and make you feel a thousand times more hurt and confused.
I am here for you along with the other members of this great forum. Keep talking to us. We do not judge.