>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4500179/
>Research during the past 2 decades has clearly demonstrated that BPD has a positive trajectory over time. Although it is a disorder associated with many psychiatric and medical comorbidities, many of the most troubling symptoms remit during the first few years. Unfortunately, several of the underlying personality traits remain for longer periods, and these are the elements of the disorder that may not be fully addressed by current treatments. Many of the specialized psychotherapies help patients with BPD, but long-term functional recovery is difficult.
Seems like studies primarily research BPD patients that get treated. If your mommy doesn't get professional help this might be why she does not get better.