It's not just that she's changed, it's that she has become completely different from the person she used to be. She's transformed into a completely different person. The audience claps for her, and the narrator thinks that's a great job. He wonders if he's bothered by how she paused when she came to the stage. He's lost in thought for a moment, and then he sees his mother again. She left the stage once, but then someone else came back and saw her. The narrator swears he saw her in the darkness.