Man, I never thought in a million years, during all those years with her that I could be friendzoned by her. What do I do? Just keep doing what I'm doing and hope for the best? Should I pursue her any?
It's entirely possible that she is, but its also possible that she isn't. However, given the fact that she is involved in an affair tells me that she is friendzoning you.
Just keep working on yourself. That's all you can do. I'll repeat the butterfly analogy again - If you squeeze the butterfly to tightly, it kills it. So, you must open your hand. The butterfly will fly away. What you must do, if you so choose, is keep your hand open in case it ever decides to alight again. If she does, great. If not, then you have your answer.
Honestly, most don't and you need to be prepared for that. You have to remember that she is on her own road and it only has room for her, not you. You most certainly can keep room on your road for her, but just know she may never travel it again. This is your road and its lined with gold. Own it.
And no, never pursue. Never.
There are moments in this life when you are so confident in the rightness of your actions, that not even for a second do you consider the option that you might be wrong.