Jean "Walters" (Slater) undoubtedly changed an awful lot over the years, from a hostile, violent, abusive, and chain-smoking parent with a severe mental illness to a meek, comedic, and airheaded character who no one took seriously. Did you prefer her character when she was dark and unstable or the caricature of childish silliness she became in her final years?

I think her changing moods and personalities is a realistic representation of bipolar as your mood, attitude, temperament and so on changes with the condition.