I just compared my Nationals and Worlds tapes. At Nationals she started the final spin sequence at 2:27 and checked out of the final spin a bit before 2:40. Her arms and upper body continued to move a bit after 2:40, but not glaringly so. At Worlds, she started the spin sequence at 2:26, but she did five or six more rotations on the last spin than at Nationals, and was still spinning with her free foot well clear of the ice after the 2:40 mark. She did not get both feet down and stopped until about 2:42.
What happened? I would guess the sort of brain lock that could have happened to anybody. The music has no audible melodic or metrical cue for the last half minute or so, being all drone and drums from there to the end. If the applause was loud enough, she might not have heard the final drum beat at 2:39 with enough certainty to do a snap checkout should she be on a roll in that final spin, while somehow thinking she had more time remaining than she actually did.
Let's not knock her for this if we have not walked in her shoes. My fellow military bandsmen and I, all experts in our craft, occasionally miscounted in routines we knew cold. Once in a great while the result was a visible or audible error.