Very helpful, Wendy. Thank you.
Part of my problem is that I am naturally an open minded person. I feel forced into the black and white world.
It’s a mess. But I need to remember she is the one wanting to make the relationship change. She is the one applying the pressure.
I can tell her I need more time to process and that is ok. She can interpret however she wants, and take the action she wants.
One of the hardest things to do was to say "no" to my BPD mother. However, she'd sometimes push a boundary in increments to the point where I felt I had to say "no". Then, she'd react as if I had hurt her somehow. That felt terrible. I would not intentionally do something hurtful to my mother.
You wouldn't do something intentionally hurtful to your wife. Nobody wants to be the bad guy in the Karpman triangle with someone we care about, but I realized that, if I was going to have boundaries, I would have to also accept that she may think that way, (but that doesn't make it true).
Boundaries are about us, we can't control someone else. If marital fidelity is one of your values, you can't waver on it in your own actions. Your wife will do as she chooses.
Boundaries also involve knowing what is "you" and what isn't "you". It's possible to be firm about monogomy and also open minded about other people's choices but know they aren't for you. In a way, your wife may have perceived your being open minded as you not having objections to her having a same sex romantic relationship. Your wife has poor boundaries. If you also don't have clear boundaries, then it's unclear for both of you.
I think what is confusing here is the incremental shift from your wife having a female friend to having a romantic female friend. If this had been a male friend, perhaps your feelings, and where the line was crossed, would have been clearer to you. It's OK for your wife to have a friendship with other females. You can be open minded about having both gay and straight friends. It's an issue if your marriage is monogomous and the friendship becomes romantic.
While I don't personally agree with the extent of what my father tolerated, it also wasn't my relationship to decide on or understand. I know it took a lot for him to be in the relationship. It also would have taken a lot for him to get out of it and also I think he knew how emotionally fragile my mother was. I see some similarities to your position here. On one hand, this could be a deal breaker but you may not wish to go in that direction at this time.
From what I can see- I don't think you are OK with an open marriage. Where you need time to process, is what you decide you wish to do about her request. You can still keep your value about monogamy for yourself.
My best wild guess is that "this too shall pass" and if it doesn't- then her sexual orientation isn't anything you could have done differently to change.