Who is Bella from History: A Novel and what is their importance?

Bella comes into the Mancusos' lives after the war has receded and when Nino has come to see himself as a rich man. Bella is a large, intelligent white dog who has been raised on the finest of foods, exceeding the quality of food that Ida and Useppe consume. Bella seems to know that Nino has left the earth, and Useppe becomes her charge and her responsibility. She guides him, takes cues from him and, if the reader is to believe the story, communicates with Useppe.