No, she HASN'T pegged it. Take an example of a classical personality disorder, probably the most negative of the bunch - borderline personality disorder. That entails sysmptoms including daily or hourly wild mood swings, attachment problems (such as becoming hysterical when a loved one becomes removed physically or emotionally), emotional manipulation, self-harm, suicidal impulses, extreme anti-social behaviour (and this doesn't mean "oh that wasn't very polite.")

People with this diagnosis have serious problems, and these are often rooted in past traumas. They deserve understanding, patience and empathy, and people who care for BPD patients deserve a bit of understanding about what they go through. Their suffering should not be diminished, and negative stereotypes and experiences do not need to be called upon for Prudence to make her point that she thought the step-daughter's behaviour is rude.

There is also a significant minority of the psychological/psychiatric community who feel these and other "Axis II" (developmental and personality) disorders are inappropriately applied. And that is amongst professionals, not laypeople.

Is Prudence a psychologist? Does she know something about the LW we do not? If turning down an invitation or not getting along with one's family is grounds for a diagnosis, I guess I didn't realise we had progressed out of Victorian times. Bring on Freud and hysterical women.

If I were the step-daughter, I would be offended that my feelings are automatically discounted as unreasonable and therefore in need of professional diagnosis on the basis of someone else's story. So yes, it does stigmatise her. But more than that, it stigmatises other people who have or deal with personality disorders, mental illness etc by bringing the topic into a negative story when there is absolutely no reason to bring it in.