Felicity, I appreciate that you are trying to stick up for this woman in saying that she is probably not mentally ill - but personality disorders are mental illnesses, they are diagnosable psychiatric disorders so I don't know what else you'd call them. Borderline personality disorder in particular is not borderline in the sense that it's not nearly a disorder; it's more like borderline as in the person is nearly always on the border or on the brink. It's actually one of the worst kinds to have. (it is a type of personality disorder, not the full name for the term as you suggest)

Some people WOULD say that 15% of the population at any given time is mentally ill - but these are the same people who think all hyper kids are ADD and any rude or anti-social behavior is a personality disorder.

I think this just goes to show you that people shouldn't throw around terms like "personality disorder" because then no one really understands. It's a very loaded term - a diagnosis, in fact - and if Prudence hadn't wanted people to "overreact" to it, she shouldn't have used it.