Death Jack in Mass Effect 2 (Mass Effect Legendary Edition)

Everyone writes that Jack either dies in the last mission, or remains alive. Now the crux of the question: I had it thrown back in the cast scene before the start of the last mission. She somehow stood behind one of the control panels, and when the beam in the cast scene hit the ship, it was either thrown back or fried - as a result, she hit her head on the table and fell dead. Why? What influences this outcome of events?