Well, I have also just watched the opening scenes again. The watch is a total red herring. She's getting dressed, struggling to put her cardigan on as the sleeve is getting stuck on the watch. So she takes the watch off, puts the cardi on and then puts the watch in the pocket.
So, proof perhaps that she is indeed forgetful (as she 'forgot' to buy the custard for the spotted dick)?
Has it been stated what sort of doctor the doctor actually is? Do we just assume that he's a psychiatrist or has that already been explicity stated?