I don't think I have come across a single SO that did not want to know about their partners CD/ TG / TS'ism. There are plenty that wish that it didn't exist (? almost all to an extent ?) but even those who intensely dislike it seem to at least prefer to know, and to have been told.
Reine's suggestion of writing stuff down until it sounds right is a good one. But I strongly believe you have to tell her face to face, no leaving letters, leaving a document or web page open on the computer, not by phone etc. You must face your fear to conquer it. You are going to betray her trust, almost by definition. By telling her face to face you will still at least have her respect. From there you have a much better chance of rebuilding that trust.
Good luck.
I, and yes, it took me 15 years to tell my wife. Yes I did tell her face to face. Yes there was lots of crying and I believe she quite possibly has never seen me that scared before in her life. And yes, we have had up and down bits (though curiously not as bad as when we were dealing with sleeping problems with our 2nd child). But overall, it has helped and strengthened our relationship.
