You just keep saying ‘yes she did’, well no she didn't, and it is idiotic to think that she was cruising around delivering goods driving a truck, yet living under high security the rest of the time.
You even admit that if she did drive a truck to a delivery for the propaganda show, that she would have had a security detail accompanying her, presumably in multiple vehicles, and involving many men (all for a single female truck driver), I would not be surprised that that had to have happened at least once for the newsreels and photographs that this charade was created to make.
Research keeps showing the same propaganda reporting over and over, nothing reveals her as a real truck driver for the five months that she was earning her Captain rank.
I am a military historian and I have studied this. Unfortunately I studied it on the other side of the planet, and I don't have easy access to the evidence I studied then, or I would go to it and cite it. I probably could, if I wanted to spend a few hours at the State Library or one of the local University libraries find locally obtainable references, but proving to you that the sky is blue isn't really worth that amount of time to me.
I keep saying "Yes, she did" because yes, she did - as tens of thousands of people have been aware of for decades, and a hit piece in one newspaper doesn't counter those facts.
As for her 'security detail' I said nothing about some massive operation accompanying here is multiple vehicles or trucks. She would have probably had one officer with her. Security for the Royal Family is nothing like what you are used to seeing in America with, for example, your President. I have actually been sitting near the Prince of Wales (himself the heir to the throne) when somebody ran at him a few years ago now firing a pistol (it turned out to be a starting gun, thankfully). The Prince's single bodyguard acted. The gunman was actually brought down by the Premier of the state of New South Wales and the Australian of the Year, who were sitting in the front row of the people on the stage. And that was in 1994 in an era when security is taken a lot more seriously than it once had been. Except for the Monarch themselves, most members of the Royal Family rarely have more than a single security officer with them - the Queen herself generally has no more than five. Remember when Diana, Princess of Wales died, there was only one bodyguard there. When somebody attempted to kidnap Princess Anne in 1974, again, she had only one security officer present. Princess Elizabeth would have almost certainly had only one bodyguard with her.
In terms of photographs, there are very few candid photographs of the young Princess and Queen because photographers did not take them, because newspapers would not buy them. Even at nineteen, the Princess was still legally a minor by the standards of the day and any photographer who invaded her privacy would have been treated with contempt by society at large.
Prince William and Prince Harry are both currently on active service and when discharging their military duties do so as other airmen and soldiers do. But when they return to their home at St James Palace, they enter a high security bubble as well. Prince Andrew did this before them for many years, having a fairly long and fairly respectable naval career. The Prince of Wales did it too, for about five years during a period when the UK was at peace. Prince Edward as well, although his military career did not go very well, it lasted a few years. And they are just the most recent examples. The Royal Family have been doing this for a long time and they know how to make it work. The Queen's father fought in the First World War. One of her uncles, Prince George, Duke of Kent, the son of George V and the brother of George VI, died on active service in 1942. Another of them, again brother to George VI, Prince Henry, Duke of Gloucester, was wounded in action in 1940, and later served as Second-in-Command of an Armoured Brigade. Royals serve - and Princess Elizabeth did so as well. Yes, they have ceremonial roles as well, but they are always, always kept separate. When service is described as genuine in the records - it was.
The Queen's war service was not spectacular nor very long, but it was genuine service. If it had just been done for the propaganda value, they could have had her in a much more glamorous role than a truck driver. She became a truck driver because it was ATS policy and practice to assign a new trainee to the nearest ATS unit to their home - and in that case, that was a motor pool at Aldershot, twenty miles from Windsor Castle.