Dean had not noticed the wolf looking to grab on to his tail. It might have been an interesting interaction if Fenrir did so. More than likely, Dean would have seen it as playing and they might have wrestled or something of the like.
Dean pondered on her words for a moment before he nodded and began to follow her. He had fought many, many things that were larger than him. But, he wasn't here to fight, not even in the slightly. If Red, and now Kat said things were safe, then well, he believed them at their words alone. Then the ground began to rumble, it gave Dean a slight cause for alarm. It wasn't enough for him to reach for any of his weapons, instead he looked around the area in confusion.