What is mrs Henry Lafayette Dubose purpose in chapters 13-15?

she asked jem to go and read to her after he cut off the tops of her camellia flowers. jem was freaking traumatised, but he still went with scout to go and read to mrs dubose for a whole month. after that, mrs dubose dies, and atticus tells the children that she was actually fighting morphine addiction, and she said she wanted to die clean and free of morphine. and she did. that was a symbol of courage.