IMHO, you need to tell her. This will eat away at you not to mention it has to hurt keeping a secret from her that has this much impact on you.
I came out to my wife of 15 years last year. She freaked at first, but once she calmed down, I answered her questions the best I could and let her sit in on my counseling sessions, was tested by 2 psychologists for gender dysphoria and other things. She could then see it is real,causes me pain and is something I could not have prevented or"cured" and not just a phase. She was more upset that I didn't tell her sooner.
It was rough for a couple months, but we love one another, divorce wasn't mentioned, my teenage sons are cool with it, and my wife and I are closer than we have been in years!
I hope you the best