I work with a few people like this. An example of a conversation from the other day:
Colleague: "How long does it take you to get to work from where you live?"
Me: "The train takes 45 minutes."
Colleague: "Are you sure? I think it takes longer than that."
Remember, this is my daily commute we're talking about...
The lady is definitely mentally weak else she wouldn't have given into PHB's insistence on something so outrageous. Either that or she is a loose character and is not entirely sure whether she does have any children (legitimate or illegitimate) or not!