Our heart goes out to you too and like others, we're so impressed by how you are growing in this. We lived a very similar situation too and can only share with you the discoveries "we" made.
We've talked extensively about the issues of violation of trust also that situations like this bring. But as we dug really deep into things we came to realize that although the "trust violation" was real and seemed to make an easy scapegoat, underneath it was something more important. These situations and the almost inevitable violation of trust that comes with them are really rooted in our worldview that we've created for ourselves to that point. Or, maybe more accurately, a worldview that was created FOR us ! There were things we didn't know. There were untruths passed on to us. When something like this surfaces it really does shake the whole foundations of our carefully constructed & reinforced worldview. And that's REALLY scary. It can happen in a lot of ways but "love" is just one of them. It was our lack of knowledge, reinforced by society around us that forced the violation of trust. Most people have no background in how to approach this any other way. What they feel is real and there's an inner knowledge that tells them they simply MUST act on that, but the "how" is missing. So we stumble, struggle with how to deal with this new part of life we had no knowledge of.
If you think about it, IF all of us were raised in an environment that taught us about such possibilities and they were not demonized, then there would have been no need for a violation of trust etc. We would have been prepared. It wouldn't have been an event that threatened to crumble the whole foundation of our worldview. We (hopefully) would have sat down from moment one and had the "guess what/who I just discovered" conversation. And things could have proceeded accordingly.
So now you are there. And you have a very special opportunity because of the pre-existing closeness with your GF.
In our situation, it was such a special thing to watch that bridge get rebuilt between the two women once everyone realized what we wished we'd all known from the beginning. That really, there was no threat to anyone, only a threat to a worldview that was questionable at best and at worst, maybe totally unrealistic. So I hope you and she can look at the wonderful potential that seems to exist for the 3 of you and let it bond you even closer than before. It's these life experiences we share TOGETHER that make our relationships so special to each other. And obviously this is even more the case (and potential) for you and your husband.
At least, that's what happened for us and we hope the same for you !