That most certainly is a skeksis! For a moment, Deet is genuinely frightened, and looks around for backup. Seeing SkekGra and UrGoh there, and then of course all the angels, including Thnisko, makes her rational brain kick back in. Even if this is one of the bad ones--and she may not be, because she doesn't look familiar--there's no way she could do anything to harm Deet here and now.

So, if they're going to be able to make friends, this is clearly the best opportunity to try. She waves from across the room to catch skekSa's attention and gives her a sunny smile (best to start as you mean to go on, right?). "Hello! Hi! Truth or Dare?"