It would be good to know what the error was that they didn't show us so that people could know one way or another whether it should have counted as an error or was a prop thing because with it all being a bit wishy-washy the public are going to decide that she got to stay unfairly and that won't bode well for her future.
Obviously, overall she is by far the better dancer but it is down to the way you dance in the dance off, or that's what it's supposed to be anyway otherwise why bother with it at all? Stupid question, I know that the reason they have it is that if they just binned the person who was bottom of the list sometimes it would be one of the better dancers. I think that happened in the past, although my memory isn't that great on past Strictly stuff so I could be wrong.