Amanda Knox's father said she has not slept much since arriving home in Seattle on Tuesday after four years in an Italian prison.
Curt Knox told KOMO Radio "she's literally running on adrenalin" as she reconnects with family and friends.
He said it will take some time before the family figures out what the "new normal" will be.
The 24-year-old and her family left Italy immediately after an appeals court threw out her conviction in the murder of her British roommate, Meredith Kercher, in Perugia, where both were studying abroad.
Mr Knox told Good Morning America that Ms Knox occasionally slips back into speaking Italian.
He said one of the things she has done since coming home is to lie down in the grass.