I thought that she was a sympathetic character.
I think that Skeeter's mother is someone who would never express in public her true feelings on the subject of racism, since appearance in everything to her. I believe that she did not agree with the general airs of her group of friends, and I considered that her real problem with Constantine, was that Constantine should have known how important this was to her. She was horrified at the prospect of her friends finding out, so she fired Constantine in order to prevent anyone from knowing. It must have taken all that Skeeter's mother had left to let her finally know. When you think about it, it must have occurred to Skeeter, as well as her mother that her friends treated her as if she were a black maid once she had cancer.