Her natural father is with her now. He was divorced from Shasta's mother, I believe.
All poor Shasta knows is she wanted to see her Daddy, her Mom & her boyfriend exploded (in anger), then everybody died and she got taken away, then Dylan went away (she probably knows he's dead, of course), and now she's with her daddy. What a mess. And she didn't look like a very happy little girl to begin with. :(