Mountains of Dreams — C.L. Bevill

Once the world was normal. The day after the change, there were new creatures galore and nearly every human had vanished. The survivors gathered together to make a new society and Sophie, a seventeen-year-old from Oregon, does her best to fit in. Desperate to find a reason for living, she travels east to Washington, D.C. to meet with the new President of the U.S.A. and finds that existing and living are two very different things. The old world hasn't really been left behind and human treachery continues to threaten their existence.