Lucky's main love interest/another main protagonist

Sweet is a thin, fragile-looking,[9] lean female Greyhound with smooth, velvety, pale tan-gray fur, a narrow, long face, a long nose, a soft, sleek, short-furred coat, a sleek, slender head, a slender, sleek, creamy-white muzzle, long, thin, slender legs, a light, slender frame, big, large, wide, soft, dark brown eyes, narrow hindquarters, soft, velvety ears, slender, light paws, a sleek, narrow body, pointed chops, white teeth, a thin tail, and a long neck.

The main love interest for Lucky

Sweet is a kind, determined, intelligent she who's quite loyal to those who have gained her trust. 

I imagine her voice being soft and sweet, calming.