the problem you have is here
I don't need to see a pscyhologist because it's not like I have a mental health problem."
She is not ready to accept she has problems, hence taking the next step to accept the problem is BPD is huge. That in itself can cause major denial and conflict. Accepting the diagnosis can then be devastating if they are not yet ready to commit to long term treatment, which the initial statement obviously precludes.
I think you probably need to work more on your wife realizing she has 'a' problem, before even trying to put a label on it. It is common for Ts to treat the problem without labeling it as it does cause an adverse reaction often leading to rejection of therapy, hence being counter productive.
I found concentrating on aspects of the disorder individually is less confronting. eg black and white thinking, and how it links to different areas in her life. Once it becomes normal to discuss these separate components, then they are more receptive to combining them under a full diagnosis. But going from "nothing wrong with me" direct to "you have BPD" is too huge a step, especially as there is no quick fix.
What you can do is work on you and in particular stop being an avenue for her projections and thus an outlet for abuse an anger. Let her self soothe, and carry her own anger and issues. That way if she is left holding her own bagage then they will become more obvious to her and she "may" go back into T to address it. That is force her to reconsider that opening statement.
Until you have got her out of that mindset, you will get nowhere, even with a diagnosis
