Most Helpful Girl
Hey, you're attractive, go on get on with your life. Sure it hurts now, so be it. Be sh*tty now, be broken. But don't ever sacrifice your pride and ego just for a girl. She's back with her ex, mister. I'll say it again. She's back with her ex. There you go. I hope you realize she moved on, and so should you. I know it won't be easy now, she left some scar, but it will get better with time.
But if you really need some closure with her. I would say, go play and sing the jason mraz song, not live, but record it, then send it to her via email or something, with your letters too, tell her how much she means to you, tell her how you feel etc, let all your feelings out on that paper. Then after that, move on, mister. Finish this chapter and turn the page. At least you already kept your promise and you did tell her too about your feelings toward her. So then it really is over. Nothing left. Remember, she's with her ex now.
Good luck, I hope my advice helps you.