It depends on what aspect of her you are talking about.  There is one thing that she definitely does change, and that is her addiction to morphine.  So whatever weakness of character or body that kept her addicted to it all of those years, she grew resolved to "leave this world beholden to nothing and nobody."  So, she does change that about herself.  But, not much else.  She was still ornery to the last, still finding ways to make Jem angry and irritated.  In fact, right before she dies, she prepares a present for Jem; it is a box with "a white, waxy, perfect camillia" in it.  Talk about rubbing a kid's face in it, after he had spent so long making up for destroying her camillias!  So, even to the very end she was sassy, full of spirit, insulting, and had to get the last word in.  She was still racist, degrading, and insulting.  But, she took on her addiction with bravery and courage, and Atticus admired her for that-despite her other faults.  So, Mrs. Dubose was quite a character, and stayed true to that character to the end, adding the additional and highly admirable titles of "great lady", "the bravest person" Atticus knew, and courageous for taking on her addiction.  I hope those thoughts help!  Good luck!