Jem was in trouble.  He had to go over to the mean old lady's house and read to her for two hours everyday.  Scout went with him for moral support.  She noticed she drooled a lot.  She then died because she was so sick.  Atticus told Jem how brave she was because of what she went through.  She had been given morphine for a pain reliever, but became addicted to it.  She wasn't going to die relying on something so she didn't take it anymore.  She mastered her goal.