She wasn't held on course with Apache Sauce. Fence four was very technical with an upright brush, doubling back 180degrees to a very narrow brush corner. There was a longer route which most took, but Mary tried the short route, and it didn't happen for her. She retired straight away.
I read this article and thought how lovely it was that Mary didn't blame him, but instead blamed herself 100% for his run-out. Also a rather amusing photo at the bottom of the page...