Can't figure out what it means."
It might well mean something, Rheo. As JJ pointed out to me many threads back, auto paint is nearly impossible to scratch to the point that one could accumulate identifiable traces under their nails.
Of course that would apply to fully cured paint. If Neil had a freshly painted car, it could be another story. Of course LE had their man and very likely didn't check into it.
Maybe nothing at all to this angle, but that blue paint under her nails had to come from somewhere. Would put my mind at ease with it, if I knew LE had at least checked it out.