Why has Zedd gone to see Addie? Why does she live where she lives?

Zedd has gone to the home of an old blind witch named Addie. Zedd wants Addie's help to learn all he can about the veil. Addie has lived in her house in the woods believing that the Keeper cannot find her there. Zedd tells Addie that the veil is torn but Addie appears to realize this.