A miracle area is a place where only one human survived The Ending. LiFe is the only place where they can communicate with other humans. They also have to do a lot just to survive. Annie is in a miracle area.
Kleya Smith's location may technically be categorized as a "Miracle Area" because she's the only one present; however, it's much easier for her because she has D to help control food supplies, her ship, and so on.