In the FM Walkthrough she makes the comment regarding her knowledge of the traffic on Batar Creek Road as per this link Underlined by me):
William Tyrrell's foster mother describes how she drove all the way to a busy road before accepting the three-year-old was gone.
www.dailymail.co.uk
"William's foster mother - who is now a person of interest in the long-running case - described how she drove all the way to a busy road before accepting he was gone after frantically checking with neighbours that he hadn't wandered into their yards.
'
The semis go down this road quite often and they fly,' she said."
.... JMO - There was no need for FM to say that about the semis, and I suggest that she has added that comment in order to validate her story about pulling over for a semi, when in fact she didn't encounter a semi there.