You spell out what this is about - fear and feeling scared. The images are a simple a way of showing your fear in a recognisable way. Also your reaction is one of fear.
In the world of dreams our most intimate fears and longings are given an exterior life of their own in the form of the people, objects and places of our dream. You are not therefore facing an exterior snake, but only an image that you create and react too in fear. Dreams are virtual realities that we create in our sleep. Even the wonderful dreams of God and angels are an external virtual reality, and mirror of our own inner immensity and our enormous variety.
Unfortunately people either accept them as externally real, or as fantasy. But they are reflections of your potential, that cannot be seen in your daily life that is so dominated by your physical senses, hungers and fears. See
http://dreamhawk.com/dream-encyclopedia/the-magical-dream-machine/.
So the images and fears we experience in our dreams are projection upon the vast screen of our mind. They are all projections from you. Running from them is like trying to escape from yourself.
That you are on a beach with your dream wife shows you are on the edge of the great ocean of your inner self, with all its wonders and fears. Unfortunately you kill out a living part of you, and it seems you did this because you carry a memory of being hurt at a very basic level. Remember that every part of a dream is a living part of your feelings, and the snake is a fundamental part that represent in most cases the flight and fight response - exactly what you did it the dream, you ran away and then fight it.
The snake is life energy and is like electricity in our house, and can be destructive and positive depending how we use it. So if we feel fear and hatred it poisons our system and can cause illness and death. If we relate to it in a positive way it can create a heaven for us. See
http://www.youtube.com/watch?v=VYYXq1Ox4skSo your dream wife was correct in saying not to be concerned, because nothing can hurt you in your dreams. All you feel and meet is emotions, and if you run and kill them then you are the less, and can run from them all your life. You cannot escape from yourself - and that is all you meet in your dreams.
Tony