Isis is the titular White Wolf of Icicle Creek.
Isis does not communicate words through her barks. In 2004, she was found by Julius McQuade and was trained by him to follow certain commands. She grew to love human interaction and even saved his life at one point by bringing him a coat, a gesture which she later used on Nancy.
While Isis does come in handy when it comes to getting into Trapper Dan's Needle, she has to be placed in a sanctuary at the end of the game, as she is still a wild animal.