What did Mrs. Dubose vow to do before she died in Chapter 11 of To Kill a Mockingbird?

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.