RedHead, I'm watching and hoping someone comes along with a positive story for you.
According to the accessible literature, it would be a very small percentage (approaching zero by some accounts) of people who are actually diagnosed that can change. Of course, there are also many sources out there that say someone can have traits without having a full-blown diagnosable disorder, and there's not much to go on to tell how likely change is. So your wife could be anywhere along that theoretical spectrum.
Until then, I had two questions that maybe will be more important in the end (I feel they were for me):
Do you have any evidence that she, personally, is capable of the kind of introspection that would be required to get results in treating a personality disorder/PD traits? I've read that few PD's seek treatment and the ones that do spend more time manipulating the therapist than looking at themselves, to the point that it's hard to even diagnose them. That doesn't mean this characterizes your wife though. I found this question useful because my WH with NP traits is in IC and SAYS he's considering all possibilities and will do anything to fix things, but the minute he's asked to answer questions other than describing factual events or repeating lines from relationship books, he lashes out with the blame and the self-righteousness. It's like he's incapable of looking behind his own mask without self-inducing a huge narc injury. He can talk about this or that behavior being wrong, but never what is behind it. It's like he's a bomb, and real introspection is the detonator. So when my therapist asked me this, I answered no. When your wife says she'll look at possible BPD and treatment, have you seen any patterns of behavior to indicate that she really can/will?
Two, are you willing to stick around and see? If it's so hard for PD people to heal, you could be living with this for a long time. Is it something you're willing to deal with indefinitely as long as you see effort? Can you move forward with a partner who is not a genuinely whole and healthy person, as long as she can keep the behaviours within acceptable limits? I thought about this long and hard - for the sake of the kids, could I dedicate the rest of my life to someone who is scary, but is perfectly happy to stay behind his mask and act nice as long as I toe the line and don't question him? Can I live in basically a fake relationship? I decided no, I couldn't. Either he addresses what is really going on or I'm going to spend the rest of my life in fear of overstepping some invisible limit, wondering when the next discard will happen. For me the bottom line was 100% and nothing less. By 100% I don't mean perfection, but complete honesty and safety. Can you live with basically reformed actions but a core personality that is still the same? Maybe you can still feel safe with her, and in that case you're braver than me.
You may never know if she actually has BPD. Either way I guess it still leaves us BS's with the same 2 questions, can we live with this? And if not, based on all patterns of behavior from throughout our relationships, is there any potential at all for real change?