Snow66! has yet to answer this point.
You generally dont get backspatter with low calibre weapons Steve,but if you do its mostly from shots to the skull where the cranial pressure blows the blood out.
Backspatter was simply introduced to suit the police scenario of someone replacing the silencer after Sheila was dead.Usually a bullet pulls everything into the wound unless it hits an obstruction like the skull.
There was no obstruction in Sheilas neck,just soft tissue,and the second bullet went straight up into her brain unhindered,so little chance of drawback.So no need for any blood inside the barrel or much if any on the outside,as the gun would have instantly fallen away from Sheilas neck.