I know it is easy for us to comment on how YOU should handle your wife... since we don't know her and all. But, here is my suggestions (some may be harsh).
1. Try not to make your carrying condition or anything about it the forefront of conversation. Strap on your gun without her being right there, put it in the condition you want, and don't say a word.
2. Educate her, put her through a formal NRA First Steps Pistol Class or something like that, so she understands gun safety a little better and has some "hands-on". The outside influence will probably help, its one thing to hear it from you, but to hear stuff from an outside 'expert' will usually do good. I say NRA because its a good standardized curriculum hopefully removing the 'cowboy element' you could get with a curriculum put together by an instructor. Get her shooting with you, even if its just a little to remove the mystery and help her understand the mechanics of it.
3. If none of that works, tell her she will just have to trust you and explain that you don't tell her how to carry her purse, or her keys, or her makeup. (sorry, the harsh one)
Sometimes you have to do what you can to educate and bring her along -- then you might have to draw a line in the sand, sack up and tell her that you have done everything you can to educate her and now you've come to and end-pass where you intend to do the right thing whether she likes it or not.
Hope this helps without being too harsh, but sometimes you have to stand up for what you believe in EVEN IF it causes you some inconvenience or distress with your wife.