Dialect can be defined as "the language of a particular district, class, or group of persons." Authors use dialect to give different characters unique personalities as reflected by the way in which they use words. Different geographic areas frequently evolve differences in expressions or pronunciation of words; when written, these differences indicate the various dialects being used. Authors may also make up dialects, as when they are creating fictional worlds and languages.
In the quote, the first sentence reflects grammatical structure - a standard English form would read that Granny always has instead of got. In the second sentence, a local dialect expression is being used to convey the idea that Granny is constantly talking without ever stopping.