Those who are living with someone who has undiagnosed alzheimers are more often than not in denial and put a lot down to getting older. In fact alzheimers doesn't often feature in the life of their loved one and they just carry on regardless.
Similarly, PND can lie dormant for many years too and also go undiagnosed until it's too late dependent on a person's lifestyle and how it could be masked by unnecessary medications.It's not always admissible by the person involved because they don't know what's happening to themselves. What is known is that when left undiagnosed it manifests itself into something more serious.
To say that those are in denial who are living with someone in the early stages of Alzheimers is grossly unfair, however, I'll accept that they may believe that little quirks are part of getting older. It's only 'after the event' that they can recognize what the 'oddities' were. Hindsight is a wonderful thing.
You've floated the PND theory for years -and I'm more than prepared to accept that sensitive, 17 year old Sheila, rather than being made to act as if nothing had happened worth mentioning, should have received counselling following her first termination- but as you've never suggested at what point you believe it set in, I'm not prepared to accept that it went back 10 years prior to erupting violently, and whilst she probably had every reason to be depressed, I don't believe PND reared it's head 6 years after she last gave birth. Whilst it's always possible that it CAN lay dormant and undiagnosed for years -after all, everything is possible- the probabilities lean more towards that it didn't.