amanda knox , 27 , and her family have been left in financial difficulties by the fight to clear her name .
biographer douglas preston claims the seattle native now suffers ptsd .
claims that the knox family have used up the $ 4 million advance she got for autobiography .
he says that despite being declared innocent last month the victory was bittersweet .
in late march , knox , 27 , and ex-boyfriend raffaele sollecito were acquitted of murder of meredith kercher in november 2007 .
pair were convicted of murder in december 2009 , before being acquitted in october 2011 and reconvicted in 2014 .
spent a total of four years behind bars while they were in italy .