STOP! No mushy drawn out letter no rehashing details.You've lived without her for three weeks now and you are still alive. She is obviously in denial right now from the guilt of her actions and its to hard for her to deal with. Let her know only that you still love her and that you want to forget what happened and start over. no more! If she wants you back and still loves you she will have to confront what happened and her part in it,apologize and forgive and get on with your relationship. If she does'nt love you and does not want you back the letter will accomplish nothing. And remember mistakes are human and as long as we learn from them and do not repeat them to often love can prevail and life goes on. Good luck kid. Grog