Why, in Atticus's view, was Mrs. Dubose "a great lady"?

Atticus feels that Mrs. Dubose is, "the bravest woman he has ever met." It is her addiction to morphine and subsequent effort to rid herself of it that has transformed her into the bitter old lady that she is. Atticus points out that any man can hold a gun and feel brave. Mrs. Dubose has the inner courage to break her addiction before she dies.

Mrs. Dubose has the "inner courage" to break her addiction before she officially-- DIES.