I think the superficial abraisions on her neck/shoulder were from her pj top. it is possible that inmate took a handful of the material and pulled Kristen towards him/edge of bed and proceeded to stab her in the back. I had pjs that were very similar and they could get twisted very easily when worn by an "active" sleeper and there were numerous times when I had abraisions (some would have said rug burn) at my neck, arm pits, wrists, waist, and ankles all form moving so much in my sleep that the pjs became tangled/pulled taut thus rubbing across the skin for some time.