Most of us on here have SO/spouses who have not been told they seem to have (or definitely have) BPD. For me, it's not a debilitating secret. It's just a piece of knowledge that helps me, but would not really help H. Not at this time, maybe never.
Whether your W is told she has it or not, in my opinion, will make VERY little difference. She will likely ignore it, and possibly turn on the T for even suggesting it, and maybe refuse to go anymore.
Knowing about BPD is far more helpful for US. It's good to be able to put a name to the behavior we observe, and to learn that we are neither alone in it, nor are we 100% of the problem (as we are often told. repeatedly.)
If you have receptive friends and family, willing to learn about BPD who can be trusted to handle things delicately, then I'd go ahead and share with them. But this can backfire, and the T is right in not wanting to simply say, "Hey Lady, you got the BPD. Snap outta it."
I feel that her insistence that there is nothing wrong with her and 100% wrong with me is related to the lack of a clear signal from the psychiatrist
^^Not really. She does not want to believe anything is wrong with her, so she won't. The T, I think, may have a good handle on this but may not be explaining it very well to you - see if this is close if you can talk privately:
Many actions a pwBPD exhibit are about dodging and avoiding shame and blame, they NEED to
not be at fault for things. When they can't escape fault, they tend to shut down, can fall into deep depression. Black and white thinking means they MUST be ALL good, or ALL bad. One mistake can mean they are suddenly ALL bad. Being all bad means people will abandon them. So they will go through all manner of mental gymnastics to avoid being in the wrong or the blame for ANYTHING.
For a person like that to have someone in authority tell them they have a condition that means they certain ARE int he wrong at least part of the time can be devastating. And they will retreat from it, deny it, vilify whoever suggests it.
If the T wanted to run her off, they'd have told her long ago.
The knowledge that it's BPD, or even just likely BPD, is meant to help YOU learn to adjust your reactions to those BOD behaviors to stop adding fuel to the fire. As much as BPD sucks, and as much as it seems to rest all on the pwBPD, WE are also just damaged enough to end up in the relationships. Many of us are codependent or have other issues like depression and anxiety that somehow make this seem "normal" for us where it has to get pretty bad for us to even look for help understanding it.
Even if the T never says a peep to your W about the BPD determination, nothing stops YOU from employing the tools and lessons to see if you can minimize the drama.
Walkinthepark mentioned radical acceptance. THIS is a big thing. Imagine your W has a physical disability. She's in a wheelchair. You can SEE she's in that chair and don't expect her to be able to do certain things, like go rock climbing next weekend - oR, you at least acknowledge that she has more challenges to go rock climbing than other people. She may be able to do it, but it will take more support, and more planning for her than other people.
BPD, the way I see it, is an emotional disability. Some coping mechanism, some ability to manage emotions, is just missing, stunted, not developed. Most people have some ability to handle things, even very unpleasant ones, without going totally off the wall. In BPD, emotions are often uncontrolled, they are facts, "How I feel today is how I always felt, so if I am mad today, I have always hated you - if I love you today, I never hated you, why would you even mention that?"
To simply handle unpleasant realities is a super big challenge for many with BPD. Hell, for my H, if it rained today and he wanted to do something outside, his life is ruined and it must be my fault.
I'm not thinking I can't get better than I am but I also don't see much improvement at all from my wife.
Improvement is relative and slow. H did not show much improvement until I made concrete changes to myself. I also have a form of PTSD, I grew up in a pretty crazy household as an only child with two mentally ill, abusive adults nominally called "parents". My knowledge of BPD came about partly after trying to reconcile internal rage at the overt abuse and the quiet neglect I faced for 19 years. I had repressed memories and dissociated feelings tied to those memories come to a head about 10 years back, right when H and I were facing a VERY turbulent time in our r/s. This site helped me greatly.
As I worked at making ME healthier, stronger, and set a few boundaries not to control H, but to not allow myself to be screamed at (as much), things improved. If things get heated - take a break. You do NOT need to be screamed at, but the answer is not changing her, it's changing how YOU react and what you will allow yourself to take. Find ways when you can to leave the argument. Leave the room, the house, find a task or a chore. With some couples, you can get away with saying, "I will not be yelled at. I am going out for an hour, a while, whatever, until we can talk calmly. I will be back, but I will not stay with you this angry." For me, such statements would fuel the fire, so I just pick an opening and find a reason to leave. Only you can feel what's best in your house.
I mentioned to others my bungee analogy. We are on a ladder of emotional coping. We are on level 10, our SOs are tied to us with a bungee cord. Day by day they bounce around, sometimes on our level, sometimes much lower, heck, on a really good day they may even bounce higher. But on average, we are steady on our level while they on average are a little below, maybe about level 5. As we work on US, we climb that ladder, with them still tethered to us. They are still bouncing away, some days higher, some lower, but as we slowly and steadily climb, and hit level 15, they are now averaging level 10 - they have improved by us taking all those steps and as they push and pull, they got dragged right along behind us.
Accept that she has a disability. Accept she may never learn its name and that THAT is OK. The name is not what's important, so much as a strategy for how YOU and you families can deal with it. You know she may quack and waddle and like to swim, but realize she will be very upset if you call her a duck.