Thanks very much hyperskeptic, for not being harsh with me (or her).
As for she and I remaining monogamous if this opportunity passes her by? I think because of our openness with one another, and the fact that she is very antisocial, I'd see a second scenario like this coming many many miles distant.
I *should* have seen this one coming, but when she tried to bring up poly with me, I got defensive and assumed that (because of my past affairs in my past life) she was trying to keep ME on the mono path, when there was never any doubt in my mind. (and I can honestly say that, after counseling and soul-searching and much open discussion about how and why those affais occurred)
By the time she bluntly hit me over the head with the blunt poly 2-by-4 (I need blunt, seeing as I have zero intuition when it comes to relationships) she was already falling pretty hard for our friend.
So if this does pass us(her) by without anything coming of it, yes I have complete trust that it will not occur again. Not without a serious disintigration of our relationship as it is now and that disintigration would be a major warning sign in and of itself.
Thanks for explaining that monogamy is a choice. That actually makes a lot of sense and I had been taking it for granted.