Ann, I think that was part of the point. She didn't know about heating a dinner between two plates or how to use that kind of tin opener because that had never been a part of her experience. Pasta, the meat ration was fresh meat or things like ham and bacon. Tinned meat was brought in from America and there was also fish and tinned fish.
I think that, like today, the ability to cook varied from person to person. My Mum was a good "plain" cook, some of my friends' mums were diabolical cooks, they used to love coming to tea at my house! My Mum was also probably in the last generation where the local baker did the baking because the gas pressure in the oven was unreliable and you wouldn't want to risk wasting the ingredients by home baking. Mary Berry didn't mention it but one of the miracles of electric cooking was the even reliable heating and the controllable constant temperature. that's why she sold so many ovens by making a victoria sponge.