Many times what a pet brings to you are feelings.  They bring those feelings that you need to connect with.  This can be past life healing that needs to occur, or simply a contract you and this pet entered into before you came into body.  There are many reasons for this type of situation.  We know none of it makes sense to you now because of your love and devotion to this dog and her love and devotion to you.  It makes no sense that one as innocent as she should suffer for you, or your lessons, but it is her journey and choice as well as yours.  She has her path as you do.  You are fortunate to have the love of such an animal in your lifetime.  And she is fortunate as well.  Learning to feel allows you many opportunities to explore love and compassion..