"Because if Hans got close enough to hurt you, it was my fault since I let him," she reasoned, and in Anna's head, it made sense. Above all else, she was horrified that someone had schemed so much to do away with Elsa, thus involving the princess who had barely spent any time at all beyond the castle grounds. Anna chastised herself for being stupid, for harm potentially caused to her sister, and deep down, really deep, she also chastised herself for wanting to know why. She didn't think she could fully stay away from Hans.
A nod then, and would let Elsa continue. Why stop her? Anna needed to hear the truth, all pieces of the puzzle, so it wasn't such a mess for her. "Alright. Tell me," she encouraged, her voice soft, even though she didn't particularly enjoy the taste all of this was leaving in her mouth. But there was nothing to be done about it now.