Sweet

Info from the Offical Site

Sweet was once a pack dog to a group of swift and agile dogs, though unfortunately she and the rest of her gang were taken and stored up in what is known as The Trap House. There she met Lucky, and quickly befriended him just before the hectic Big Growl occured. She soon after yearns to become a pack dog once again, and sets out on her own to find one.

In the Second book, Lucky reencounters her when he spies upon a fight with Bella's pack and an unknown pack. He finds that she is the new beta of a pack headed by a half-wolf dog. She commands great respect among the pack.

Description
Sweet's a speedy, agile dog who's great with orders. She is very resourceful and commands great respect among her pack. In her physical appearance, she is a small dog with short grey fur.

Trivia

 * It is hinted that Sweet may have feelings for the Alpha of her new pack, but it is not certain. She has stated that they are partners and not mates, though they may become mates eventually. It is also hinted that possibly Alpha does not have feelings back for her, or does not realize her feelings towards him.
 * When she joined the pack, she apparently "worked her way up the ranks quickly", as said by a few fellow pack dogs.
 * It is revaled in Storm of Dogs that she has feelings for the alpha in her pack.