Well... She's already considered the idea of losing you forever in the past, when she decided to cheat. There is something missing for her in being faithful to your OLD marriage. That's why you have to show her that it will be a fresh, new marriage with a very bright future. (I think that's why she wants a wedding - a new beginning to something a bit different than she experienced with you in the past.)
It's not just come "home" (likely boring for a girl who wants the fantasy like your W), it's come to the even better man I am now and have all of your dreams.
All of this negotiation, talk, and promises probably aren't exciting enough to close the deal for her. She might be afraid of living numb in a less-than-satisfying life.
All you can do is be the great guy you are and work on yourself (reading, self care, GAL, etc.) Offering her a better life, a better marriage with work and dedication to improving things to make her happy is the perfect gift. She has to believe it, I suppose.
