Hi Julie. I hope so much that you and your wife can find a way that makes you both happy. I know the pain of having to choose, and it's so so hard.I just thought I would add a happy example of a relationship working out, hopefully it can help give you a bit of hope.
I waited almost a full year after discovering that I was FTM before I told my partner (straight cis male) that I was trans. To be fair, he was immediately very supportive and kind, and wanted to work on ways that I could be happiest. However, over time as the reality of it set in, we became more and more worried about what our future was. We love each other very deeply, but he is a straight man, and there's no fault in him not being sure if he could love a man. What I eventually decided on was that I would not come out and not transition so that I wouldn't lose him.
That was around a year ago, and it's been incredibly hard. I've worked on coping mechanisms, and he's been faultlessly compassionate and understanding, but it's never been enough, and the sadness and yearning has been escalating more and more over time. He, rightfully, had a lot of fears: he worried about losing his family, his close friends. He worried that I would transition and he would no longer be attracted to me. We talked about it many times, but we could never really get somewhere that felt like a good answer.
Finally, after a long hard year in hiding, we've found a way that works for us. We're still making plans and deciding how we will approach things, but I will be able to come out publically - my partner wants me to be happy, and he has decided that he is fine with socially identifying as a man in love with a man. Whatever pushback we are going to face, we're going to muscle through it together. What we've realized is that our issues are much more centred around medical transition, and this is where I've learned that I am able to compromise. I won't be taking testosterone or pursuing surgeries, but I will be living as a man, and will be able to do other things to create the image of a male body. Top surgery may eventually be a possibility, and I'm hesitant about bottom surgery regardless.
Anyway, sorry, that's a long-winded response, but my point is that we felt like the situation was totally hopeless, and eventually we found a way. For us, it became a matter of breaking the entire matter down into pieces and addressing each one individually to see where we stood. He doesn't feel he could be attracted to a man with a penis, but is completely comfortable with a man with masculine features and presentation, etc etc. I feel that what you're up against is very difficult, since it is the general discomfort with the concept of "transness" itself that seems to be troubling your wife. But I truly hope that, over time, she'll be able to evaluate those feelings and find places where she's able to meet you in the middle. It worked for me, and I have faith that it can work for you.