Blythe thought she was going to get sick and had to close her eyes. If Vader was being entirely forthcoming, he was training the dragon in Asgard. And it wasn't a well-kept secret that Blythe was terrified of larger animals. It was true that not much was known of Myre, other than the fact that she seemed to be a cantankerous sort, but that wasn't what soured her mood.
What upset her, really, had to do with a conversation she and Vader had several months ago - one where he all but said he disapproved of Metatron's means of leadership. "You of all people should know better, Darth Vader." She said harshly, "If that is indeed what you mean. For someone who speaks so highly of himself, you make the gravest errors."