Hi Shy,
I am so sorry that you have been dealing with this situation. It is not an often discussed part of BPD, but hallucinations and delusions are very, very common for pwBPD. Research has found that psychotic episodes with BPD are not only common but frequent and tend to persist over time. Auditory hallucinations are the most frequent form of hallucination experienced by pwBPD. Here is just one article about the phenomenon:
https://www.psychologytoday.com/us/blog/the-science-mental-health/202208/hallucinations-about-harm-in-borderline-personality-disorderIf you do a Google search on "BPD hallucinations" you can find many scientific studies from the NIH and other medical organizations that go into much more detail. My dBPDw hears voices that tell her negative things and it often fuels her dysregulation. The good news is that medications can help with these very debilitating symptoms. The challenge is to get the pwBPD to realize that they have a problem and need to seek psychiatric treatment. Just like other disorders that have psychotic episodes, these voices will not last forever. However, without medical treatment (usually a medication with antipsychotic properties, not just an SSRI), they are likely to return again and again and be chronic. I am currently trying to get my wife to go through with her expressed desire to see a Psychiatric Nurse Practitioner and am hoping against all hope that she is prescribed a medication that not only stabilizes her mood, and treats her anxiety and depression, but also limits or stops the psychotic episodes.
Unfortunately, like most things BPD, the duration of this hallucination/delusion is completely unpredictable. She may "come to her senses" tomorrow or she may persist in her beliefs indefinitely. Please keep us updated on how you are doing and how the situation is evolving. Also, remember to take care of yourself. You have no control over her situation, but you do have control over yours. Remind yourself that you didn't cause this, you can't control it, and you can't cure it. Give yourself some grace and do some self-care. You can't be ready to help anyone else if you aren't caring for yourself.
Keep in touch,
HurtAndTired