That said, I suspect the P is not clueless as to the BPD, because if the P was, your wife would be sent home with other meds like Lithium or Seroquel. Antihistamines are a relatively "safe" way of treating anxiety without the addiction issues of benzos. P may simply be listening to anxiety complaints and treating her in the safest way possible.
Wife has been on Depakote for 7 years now for bipolar dx.
Is there an option to try a different P? As you say short infrequent vists are not all that hard for a pwBPD to lead medicos down the wrong path. What does your wife want to believe she has?
I have hoped she wold find a different P for years. P tells wife she is bipolar and not to seek a T because she sees no value in it. "You are still bipolar. Here's your script(s), see you in 3 months." does not seem to be due diligence in carrying out her duties as a physician.
Again, and fortunately, wife found a T she really likes and sees weekly as a condition to me not filing for divorce a few months ago.* This T is the first one who seems to get she is BPD and is making some good progress.
* Did not want me to file for divorce, but threatens to leave me weekly. Ah, the life of a non... .