if it's simply the case of dear friends who love each other undeniably, eloped and were quickly married - wouldn't disfellowshipping be way overboard?
yes we 'fornicate' wonderfully and often
Missed this earlier.
One of the primary guiding factors to life in JW-world:
Any JW can be disfellowshipped at any time for any reason 3 JW elders agree upon.
That's not hyperbole.
If / when the JW elders find out you were "fornicating wonderfully and often" prior to marriage, she almost certainly will be disfellowshipped. JWs are disfellowshipped for failing to "demonstrate repentance" for what are deemed "serious sins" (and that most certainly fits the description). Doing it often, and not immediately confessing, will almost certainly be seen as "not repentant" *. That, and the elders will want to make an "example" of her to discourage other JW women from seeking non-JW mates.
Even if she never confesses and is never found out, she will be "informally shunned" as I wrote in my earlier post.
There is a 99.999% chance her life as a JW will effectively be over if she marries you.
Again, if she's fine with that, more power to you. But the loving thing to do on your part is to make sure she is making an informed decision.
* A note on the JW view of "repentance": JW elders are trained not to just accept the words "I repent" as evidence of repentance. You can swear up and down and back and forth and sob uncontrollably about how sorry you are- doesn't matter, JW elders are trained to not "fall" for that. They will look at the person's "life course" - in other words, does he / she demonstrate repentance by their actions? That's what I mean when I say they elders will almost certainly deem her "unrepentant".