So are we not talking about Elsa’s reaction in this moment?
Throughout this entire film, it’s made clear that Elsa’s powers are connected to her emotions. As Elsa tries to run away from her kindom after being locked away by Hans, the storm of her creation is going at an intensity not yet reached in the film. When Hans tells her that her sister is dead, by Elsa’s hand, Elsa denies it. Then she accepts it as truth and collapses.
When Elsa collapses…the storm gives one last gust and then stops. Meaning that Elsa has quit feeling or that she is feeling too much.
Because of the wind stopping, there’s a good chance that Elsa heard Hans pull out his sword behind her. But by that point she didn’t care if she died or not. Anna was dead and it didn’t matter that she would soon be as well.