If you really have been on HRT for a year you may be heading for a difficult time. Trust is a difficult thing to gain but so easy to lose. She will find out and it would be better for her to hear it from you. In my situation I told my wife I will not do anything without her knowledge. I'd love to begin HRT but my wife is not ready for that. Shes in the bargaining and depression stage and I'm hoping we reach the "acceptance" stage. That's where I'll tell her I am starting HRT. Being TS is a huge secret and your wife may view it as just another lie. She married a man remember.
I love my wife dearly but we still, in the end, may have to split. This is all too often too much for any spouse to handle and I understand that. It seems you understand that and are prepared for the worst. I didn't see anything about children so that's good as that is another complicating factor to deal with.
My wife will have to accept each stage (HRT, FFS, GRS...) before I begin the process. I know it will slow me down, but that is fine for me if we stay together.
Good luck, I do hope it all works out.