I don't know about Sheila having been the " white witch " that she'd purported to have been when she told Helen Grimster that she was one. A " Witch-Finder " would have used the methods of the burns which were found on Neville. Severe beatings pain and humiliation. The method used in witch-finding were marks inflicted with a hot iron to see if the victim was guilty or innocent.If innocent,the marks wouldn't draw blood,if guilty of course they would bleed. These were marks " of the Devil " which were inflicted,so both Witch and Devil ensued. Another method was " clawing " of which were also found on Neville's forearm,both injuries initiating obedience and service.
Strange how the last victim of the Witch-Finder was in Essex in 1945,where Matthew Hopkins had executed his last victim by driving iron rivets through a woman's body so that she wouldn't escape from the grave.
Sheila may at one time,have read about witches in that particular area,although they frequented the country in most areas but it was Hopkins who'd made sure that they didn't survive long.