She is therefore older than the world. She can remember when the sun and the stars had not found their places in the sky and when the moon had not discovered its own power.

It does not say in any source who the Volva really is or where she comes from. I don't think she is a god like in Christianity. You don't need to know who she is because she is so noble. I would rather think of her as a storyteller, because someone had to exist to tell about how the world was created. When the Volva talks to Odin  she comes out of the ground. And when she has told her story she sinks into the earth again.