Unbeknownst to Jem and Scout, who hated Mrs. Dubose because of the insulting remarks she hurled at them, the old lady was a morphine addict. She had been taking the drug for years as a pain killer after her doctor prescribed it for her. It was the drug that made her so irritable to everyone with whom she came in contact. Atticus understood this, so he was not offended by the remarks she made about him. He considered her "the bravest person I ever knew" because she was determined to kick her morphine habit before she died. For this reason, Atticus ordered Jem to read to her each day, because he knew it would help relax her and take her mind off going cold turkey.
Jem and Scout have many run ins with Mrs. Dubose. The children don't like her at all, and when she makes a nasty comment about Atticus defending Tom Robinson, Jem messes up her camellia bush. For his punishment he has to read to Mrs. Dubose, which at first he refuses to do, but Atticus tells him he has to do it. Scout does along with Jem as he reads to the old lady. When they first go there they have to leave when an alarm goes off, and they realize that means it is time for her medication. Each day the alarm goes off later and later. What the children don't know is that Mrs. Dubose was prescribed morphine as a pain killer. She eventually became addicted to it. After Mrs. Dubose dies, Atticus explains to Jem what was really going on.
"She said she was going to this world beholden nothing and nobody. Jem, when you're sick as she was, it's all right to take anything to make it easier, but it wasn't all right for her. She said she meant to break herself of it before she died, and that's what she did."
What is so amazing about this is that Jem disliked Mrs. Dubose so much, but in the end he was the one to help her die the way she wanted to. She was free of being dependent on any drugs or anybody and that is exactly what she wanted. Despite his dislike for her, Jem was the biggest help to her. He was exactly what she needed.