margaret bates is haunted by horrific murder of 17-year-old kelly-anne .
mum-of-three says she ca n't read autopsy report which details 150 injuries .
speaking for the first time after being left traumatised by death .
teen 's boyfriend , james smith , 49 , was jailed for life after 1996 murder .
jury offered counselling after hearing of the youth 's unimaginable ordeal .