Corrected entry: In the midst of the battle, Ron and Hermione are confronted by Nagini. In the first shot, they are on opposite sides of the snake, however, after some cuts of Harry and Voldemort dueling, they are on the same side of the snake running down the staircase together.
cfitzy92
26th Jul 2011
Correction: Since we are shown cuts of Harry dueling Voldemort, it is completely feasible that they were able to get past the snake in those few seconds.
kristenlouise3