I've read thru all of this.
1) She is still "active" and has even pioneered in the past recently.
2) During this time, she has been in a (unmarried) sexual relationship with you for two years.
3) The two of you have now married, and she is considering confession to the Elders.
If this is correct, I believe if she tells it like it is (like it is stated above), she WILL BE disfellowshipped. Latest info on on-going sins (2-years kinda qualifies, don't ya think) is that one cannot suddenly find remorse and prove "works of repentance" enough to be "forgiven by the Cong" and only be disciplined by "reproof" -- which can by private -- to her alone; or public reproof -- where an announcement is made to the Cong that So-and-So has been reproved by a judicial committee but remains an active member of the Cong.
Two years screwing around? She'll be disfellowshipped. It will likely be AT LEAST a year before she can request a meeting with those Elders to consider being "reinstated" into the Cong. She will have had to attend EVERY meeting, sing the songs, study (underline in) her Watchtower, etc etc (BUT NO SPEAKING TO ANYONE). Expect reinstatement to be at least 18 months, but more likely at least 2 years, especially since this is not her first offense of formication. They will not suggest she leave you or divorce you because marriage is "holy" even if it is with an "unbeliever".
It probably would help if you attended and feigned some kind of interest. Say like, the reason you were attracted to her was because of her high morals which are a result of her religion. You realize how terribly you damaged her relationship with Joe Hoover and you feel really bad about it, too. But then they'd probably suggest a Bible Study for you with some Elder.
The alternative action is to lie and say the "dirty deed" only occurred ONE TIME and she insisted you marry each other to "make things right" and that she is crushed and so repentant and beg forgiveness. THAT would have a good chance of yielding only "public reproof" with restrictions from commenting, etc for 6-12 months.
She probably does not want to LIE! OMG! That's such a major sin. Of course, boinking dozens of times over the past two years didn't seem like a big deal. But lying does. (That is certainly a "Ya can't fix stupid!" kind of reasoning, right?)
Psalms 32:5 says to "confess your sins TO GOD". It does NOT say to confess to 3 elders. If she considers that, she may decide that she has already confessed to God and these 3 men do not really deserve the whole story or the full accounting. JW's claim that you must only "tell the truth" to those deserving to know. Psalms says GOD DESERVES TO KNOW -- CONFESS TO HIM.
James 5:16 says to "confess your sins to one another". JW's twist that to mean that you must confess to the Elders or "Older Men", but note -- that is NOT what James wrote.
Good luck! Hope it goes well for both of you!
The greatest revenge is living a happy & successful life!