My mother began a pattern of expelling and eliminating people from her life. In this she had form with her own family. Friends, co-workers, neighbors, it didn’t matter who it was. Eventually they would all do something to “betray her” and then they were cast out of her life, never to be spoken of again except to belittle and humiliate them.
Looking back I am convinced that she had equal parts bipolar disorder and chronic narcissism. The nadair for me occurred when I was 11, when my parents were still together. I was being badly bullied at school and my parents had not provided me with the skills to deal with the situation. Somehow my mother found out and all hell broke loose. She marched into the school the next day, a private Catholic boys school, and she set it on fire in a figuritative sense. The school went into blind panic mode while I watched on helplessly as my world crumbled around me. Back at home she was triumphant at how brilliant she had been, at how she had “given them what for”. She would extol her brilliance in this matter for years to come.
You don't even need as rabid a single mom as this example to have a complete high-anxiety mess on the verge of BPD or NPD.