Hey prodigylife, glad you joined us

and welcome to the boards.
15 years is a long time to cope with a BPD relationship. Did you notice issues right away, or have things gotten worse over time?
It makes sense that because you love your wife, you want her to be well. One of the challenging things about BPD is that because shame is a part of the disorder, it is really difficult for a pwBPD (person with BPD) to accept that he or she has a mental illness issue. It is too much shame, and so the pwBPD might instead turn around and blame you: "I'm not the one with the problem; in fact, you're the one with the problem!" So it isn't surprising to hear that your W denied that she had a problem.
It's really important to remember that people get help for problems that
they think the have, not for problems that
we think they have. Fortunately, there are ways to work with this -- but it can be unintuitive.
An incredibly helpful book on exactly this topic (how to help a loved one get into treatment) is called
I am Not Sick I Don't Need Help! by Dr. Xavier Amador. His brother had schizophrenia, and Dr. Amador recounts both his own failed attempts to convince or force his brother into treatment, and his more successful attempts after he radically changed how he interacted with his brother. I'd highly recommend you pick up a copy -- your local library may have it, or a bookstore or online (I got mine at a local bookstore).
...
What do you think your wife would say the problem is, from her perspective?