Strange that the knife used in the poor lass's killing had Foxy's dna on it, oh forgot she lived there, and admits repeatedly using said implement in preparation of foods.
Don't think we will ever know the truth, but do not suggest Foxy is innocent.
Lucky it is not a crime to look evil or to kiss and cuddle, definitely guilty on those terms then.
If the knife as you state was never at the house where the murder took place, then no murder could have happened with that knife. If as you say the knife belonged to Knox, then her dna must be on it by default.
The only expert witness to address the knife wound stated " the shape of the knife does not match the shape of the wounds to the neck "