As I said, I can't begin to imagine HM's thoughts at that time, but asking her to separate the Grandmother from the Monarch, would be similar to asking the parent of a dying child, to forget they are parent, it would IMO be impossible. She couldn't win whatever she did, nor could Charles, if either had returned to London without the boys, it would have been 'cruel, cold, heartless... those poor abandoned boys, this is the family poor Diana escaped from'. If they had returned the very first day, with the boys, it would have been 'those poor little boys, you'd have thought they would have kept them in Scotland for a while, out of the glare'.