I agree with AllDogBoots. I had one yorkie for almost two years before I chose to get another, and I can tell that he is much happier now with a friend. They are not crated, but we put them in a large bedroom with laminate flooring when we are gone, and they have a great time together playing and sleeping all day.
I would definitely think Belle would enjoy having a playmate to keep her from being bored. Remember though, dogs live in today... not yesterday. She is most likely over the loss of her buddy, so don't worry too much about her
