Giulia was an original character in the beginnings of Cars 2. She was to be a double agent that met up with Mater. But Giulia was left out of the completed movie and replaced by Holley Shiftwell. She is modeled as an Alfa Romeo-like car, resembling an Alfa Romeo Giulia Spider.
In one of the earlier incarnations of the movie, Pixar had a character named Giulia who was basically a double agent; she connected with Mater, and the two of them later went off and had their own adventures and met up again with the other characters at the end.