"Istanbul, city not enclave."
What in the world does he mean by 'we'? They are a bunch of freshmen doing a supply run on orientation day, not an alliance. Maybe he's... trying to build a sense of group identity? A little rude, but it would be much ruder of anyone else to explicitly correct that point, so he's got everyone giving the appearance of tacit agreement which reinforces that group identity... Well, she's on to him, that is not going to work on her.
(Also, he's doing it when he doesn't know anything about her skills or affinity other than that it might be artificing, which suggests that he's desperate, which suggests that he's got an affinity for basketweaving or something similarly useless inside the school.)
"I am considering artificing, yes." she says, putting that tiny bit of extra emphasis on the singular so that anyone paying attention knows that she knows that this isn't some big happy family. Happy families don't exist, especially in the Scholomance.