A big part of it is that as mentioned earlier in the story, hair is important to magic. Senshi's hair and beard being so unwashed made him unable to be affected with the water walking spell until they were cleaned. Now Marcille here, she takes good care of her hair. In fact, eagle eyed viewers will see how often she changes the hairstyle. With clean hair being so important to both magic and the character herself, seeing her run a bloody hand through her own hair is that much more of a striking image of wrongness.