What you are going to have to do is to prove to her that you were on your way out of the marriage anyway, she feels like she is the reason for you leaving and you have to show her that isn't the case. Also you shouldn't delay filing for divorce if you feel the marriage is over, this will show the other woman that you are serious about leaving and that it had nothing to do with her. She may not want to have anything to do with you until you are free so you are going to have to find closure within the marriage so that you can give the other woman your full attention but it's never good to start a relationship with someone else until you get closure and get rid of the old baggage from the old relationship. She may consider giving you a chance if you are divorced and show her that even without meeting her again you were going to leave your wife.
Allow her some time if that is what she needs, she is feeling guilty and doesn't want to hurt anyone because she doesn't want it to come back around to her, explain to her that you don't see her as a mistress or a fling and that you have feelings for her but do not go to her and say that to her until you are divorced from your wife this may be what she meant by not causing your wife any grief. When you can't get over someone you love, your life is in a real state of uncertainty, the worst thing you could do would be to go into another relationship only to find that it too doesn't work because of your problems. So to help you move forward, you need plenty of thinking time to sort out any issues and you need to reach that point where you can accept that the marriage is over and then follow through with divorce proceeding and leaving the other woman alone until that happens. You have to do the honorable thing here because if you do not then the other woman would go into your relationship thinking that the same thing that happened to your wife will happen to her.
You have to make sure that there is no chance whatsoever, that your marriage could be saved. If you didn't have counseling as a couple, you should explore that as an opportunity of repairing your broken relationship or at least leaving on good terms. There have been many examples of couples who have had difficult times, yet have gone on and enjoyed extremely happy lives together simply by enlisting the appropriate help. If there is a glimmer of hope that your Marriage can be saved, you should explore that opportunity but if not then move on the right way and do it the right way. The course of true love never runs smooth, but you deserve the very best that life brings you. If that means having to move on and find someone new, so be it. If it's over, you need to accept it and look for someone else to love. If it means getting back with your ex, well then go for it but not until the marriage is dissolved. There is a true saying and that is - "some things are meant to be." Hopefully, play your cards right and you will never have to worry again that you can't get over someone you love.
It's very important for you to explain to her everything if you haven't already, it may shed some light on your situation and she may be more apt to accept that your marriage was over before it even started. The only thing it changed is the suggestion I gave you about counseling if you feel the marriage is over and has been for a while then why stay in a marriage you are not happy in, you have put on an act for long enough and you are yearning for that feeling of being wanted and needed by someone. Your wife has not made you feel like this in quite some time and these are things you need to explain to the Soul Mate. Marrying and finding your soul mate is a wish every human being holds deeply. Going through life without being able to experience true and fulfilling love is an empty life. It really depends on how much longer you are willing to go without your soul mate plus the fact that you live so far apart this may be another major fact in her decision so you will have to think of how you can get closer to her if you leave your wife.
It is very important to find your own needs and desires and to have someone to share that with. It is almost impossible to have a relationship work if the two people involved do not share basic common grounds. I suggest you follow your heart and final find happiness in your life no matter what that happiness is it's important to feel that in life when you have felt like you were going with the flow for so long and living a false type of love for so many years. You have to make sure you do whatever it takes to prove to your soul mate that she is the one for you and that you have lived with regrets long enough and now you want to live a full and happy life with her. If you think my answers have helped please click the green accept button so that I can get credit for my answer and if you still need my help click reply it is free.