Sorry, but we see Justin later. At least one franchise with the word "Star" in it was going to get mentioned.
I would like to claim that Grace's reaction in panel two was my cleverly re-establishing Grace's general good nature and innocence for the purposes of this storyline.
The truth, however, is that all I was thinking when I wrote it was "this assertion of talking during the movie CANNOT go unchallenged", and all that stuff about it being appropriate for the story and general characterization was thought of in retrospect.
Fortunately, it is in character for Grace to be shocked by that. Specifically in a theater, mind. She's more relaxed about it at home, though she has her limits if the movie is new to someone watching it.
These are all important details, I assure you.