Hi Angel----are your friends considering getting another dog soon? If so, this might be a good time to do so. If not, I suggest they give the lone dog more attention. More short walks, playing with a ball or favourite toy, more grooming. Keep the dog as busy as possible and everything positive. Maybe visit friends who have dogs.To stop the chewing, give a nice big knuckle bone, this should keep the dog busy for hours and will satisfy the chewing urge.