Knox once again faces a lengthy prison term for the 2007 murder of Meredith Kercher, her British roommate, in the apartment they shared while both were college students studying in Perugia, Italy.
"It really hit me like a train," Knox said on ABC's "Good Morning America." "I did not expect this to happen. I really expected so much better from the Italian justice system. They found me innocent once before."
Knox, 26, returned to Seattle in 2011 when her conviction was overturned; however, prosecutors won the latest legal battle at her retrial. Knox did not attend the proceedings and vowed not to go back to Italy.
"I am going to fight this to the very end," Knox said. It's not right and it's not fair."
Friday's conviction will be appealed, Knox's attorneys have said. Knox maintained her opinion that Italian prosecutors had presented a chaotic and flawed case that drowned out the truth about her innocence.
"The evidence and accusatory theory do not justify a verdict of guilt beyond a reasonable doubt. ... There has always been a marked lack of evidence," Knox said in a written statement.
The Italian court Thursday also convicted Knox's Italian ex-boyfriend in Kercher's death. Raffaele Sollecito was detained by police in northern Italy after the verdict was announced Thursday.
His passport was flagged so he would not be able to leave the country. Italy's ANSA news agency said Sollecito was staying out of sight with his current fiance at her home.
Sollecito admitted he had recently traveled to Austria but denied he had planned to flee Italy.
Knox told ABC one of her first concerns upon hearing Thursday's verdict was what would happen to Sollecito.
"He is vulnerable and I don't know what I would do if they imprisoned him," she said. "It's maddening."