Although her tone was firm, there was no rebuke in it. In fact there was more of a tinge of exasperation mixed with no small amount of caring. She had known the moment Castiel learned of Morningstar's presence within the city that he might react accordingly. In fact were she not present, she had little doubt he might have attacked the fallen angel outright. Which is partially why she was glad it had come to pass in this fashion. Who better to keep the younger angel from doing such a thing than her, after all.
Turning a bit in the pew, so her back was to Morningstar for the time being and she was facing Castiel directly, her gaze met his and her expression softened a bit. I do not expect you to understand, little one, but do try to calm yourself. Morningstar as no intention of making a bid for Sam Winchester in this place. This is not Earth and therefore not the planet over which Morningstar plans to someday rule. She is simply here, as I am, to relax and enjoy herself a bit.
A glance over her shoulder at the fallen angel in question and she added with bemusement, Perhaps a bit too much enjoyment, in this instance. Then she looked back to Castiel and lightly touched the seat he had been accompanying before sliding away from them both.
Now come. There is no need to fret and certainly no need to consider openly attacking another. Not today, and certainly not in this place.