I have to say, that 15 months out of a 30+ year marriage isn't very long at all. She is still there, that's great, as long as you want her to still be there. Also, coming out to the world, being full time, changing your name, all in that space of time, is a lot to take on.
As others have said 'acceptance' doesn't mean 'sharing the joy'. Look at it from your wife's point of view. She has had a husband for most of her married life. Now she doesn't. What is there for her to be joyful about? Was your marriage awful? Were you a bad husband? If that is the case, then, yes, that is something to be happy about, if you have become and all-round wonderful human being and a great partner to your wife. That is a positive, but to her you are not the person she married. She's having to get to know the real you, all over again, while grieving for the old you. And we all know that grieving is a long process.
I agree with Tonya, positive steps in transition, to the partner, are like another step away from everything she has known. Every small step my partner takes, breaks my heart just a little bit more, every time, and he is aware of this, and tries to take things slowly, discusses things with me, and hates that he is hurting me. Your wife didn't sign up for this. She didn't ask for it. I suspect she didn't want it. But she is there, she is trying, and it will take more than 15 months to work through it. If she didn't love you, she'd be gone already.
Please give her more time.
Syl