RORY: I’m really sorry I didn’t tell you about this before, but Tristan …
DEAN: Is playing Romeo to your Juliet. Yeah, I heard.
RORY: But he wasn’t even in our group at first, but then no one else wanted him, and then Paris moved the rehearsal spot to here, and she did it today and I didn’t have time to tell you.
DEAN: You and Tristan wind up thrown together a lot at that school.
This is exactly the second project Rory has had with Tristan – hardly getting “thrown together a lot”. And it’s the first one where she and Tristan have had any major interaction. Dean is probably thinking of the school dance (which the entire class was eligible for), and Tristan asking Rory to a concert (which is hardly the school’s fault).
Dean is being unreasonable, but Tristan does have a history of making difficulties between he and Rory, and his intuition is probably telling him something doesn’t feel right in this case.