I also asked my partner to give up his SO in the beginning. He was also sad, very sad and although I know he really tried he was never the same. It took a couple of months but in the end I told him to resume the relationship and that's when I really started learning about polyamory and how to make it a positive thing in our life, even though I didn't feel the need for another partner myself.
I started a blog about my experience(link in signature) and it might be helpful for your wife to read.
Our relationship is now very good and I have a great relationship with his SO (although not sexual). I do think however, that it was important to me that he did honestly try to be monogamous and relegate her back to just a friendship status. I suppose that was easier for him because she is long distance, although he still found having her just as a friend difficult and for those few months had little contact.
I know it's going to be a difficult time for you because we've been through it, but if your love for this woman is really as strong as you say it is, I'm sure your wife will see it and appreciate the efforts you've made to work on your relationship with her. Be patient, let your wife comfort you and vice versa and keep communicating honestly.
Don't be tempted to cheat that will make everything worse, much worse.