I agree with Lou on this...it needs to be addressed or you will both be walking on eggs for a VERY long time and women dont ever forget anything. Just because she hasnt said anything doesnt mean it went away. obviously she has been stewing on this and it has been bothering her for a very long time.
And in all fairness to your love for her, you need to encourage her to go do what she needs to do to get peace and clear her conscience. But she needs to know that that is not the decision YOU made with regards to your own "confession" and laying yourself bare to God was sufficient to you and re-playing it all to the elders would mean following their pharasaic sheep controlling rules which you arent about to do. But if she decides NOT to go to the elders, she has to know that the subject CANNOT be brought up again in your marriage and has to be a closed issue. Done deal. Fait accompli.
I have...well HAD...a very close friend as a JW. She was a rabid JW and a pioneer. However she married a "safe" JW man who was always more interested in fishing and being by himself than he was in her or their kids and she was basically alone in the marriage. And she confided in an elder, they fell in love, started having sex and got busted. Well neither of them was DFd. They were split up into different congregations and told never to have contact again. But they snuck around anyway because they were in love (she told me AND he told me...this) He ended up getting a divorce. And she stayed in her marriage. But many years later there were still things about that whole affair she hadnt told the elders and she couldnt live with it. Even though she was not DFd for the sex, when she went and confessed the remaining things...probably the post JC activity, they DID DF her for like...a year. But at least she can move on now. And that was the important thing to her, to have a clear conscience before her God.