jiang shi physiology: stiff joints since shinshii is a jiang shi her joints stiffen to some degree while he sleeps , forcing her to hop around whit her elbows and knees looked at straight out, for this reason shishii practices tai shi day and night , allegedy  whithout ever skipping a session however even that doesnt always help if it's too cold in the morning and her knees and elbows stiffen anyway, immortality since shiishii is undead she cannot be killed against by any of known means 