‘ And before they were laid down (or ‘slept'), she came up to them on the roof.'
This may mean after they had been first hidden, but before they laid down finally to sleep (compare Genesis 19:4), or be referring back to a conversation which took place before they were finally hidden under the stalks, she having left them for some reason and then returned. The telescoped descriptions hid far more detailed happenings for at present they were in little danger and would not just lie under the stalks all the time. It possibly indicates that she had had time to think and had come up with an idea.