Dude.. from her email, it seems like she is guarding herself. You can tell she doesn't want to 'fall' for you.
Get her number and give her a call. Don't sound desperate. Just let her know that you've never felt that way about anyone but her. It sounds to me like you went overboard in the first place when she 'cheated' on you. How old were you? High school?! That's a time where you're just supposed to be dating anyway. You weren't engaged or anything. Big whoop. You're supposed to date around... In high school, they always try to act mature and have these long relationships.. which are CRAP, btw. Long relationships are for the last years of college and the first years of working.
You oughta call her. If you don't, you will set yourself up for wasting half your life. We've all seen the movies where two people in their late 40's fall in love again and lament about how they should have done everything when they're younger.
Give the girl a call and be yourself. And show her that you're not the unconfident dweeb that you were in high school... and show her that her 'cheating' on you really should have been taken more lightly.
Invite her for coffee or something. Find out if there's anytime you two will be in the same area.