what happened to corrie when she began trying harder to take care of betsie and protect the two of them?

I don't recall anything happening to Cory. She goes after a guard who slaps her sister but her sister restrains her. At the end of chapter 13, Corrie grows gloomy and loses her sense of joy. The misery and pointless suffering wear Corrie down as she searches desperately for a greater meaning. At the end of the chapter, Corrie is alone and miserable without Betsie, who is her best friend, nearby.