"Well, alright, if you're sure." He backs away from the stall, waiting for her to catch up before he'll give her a look out of the corner of his eye. "Have you ever haggled before? I'm not trying to assume or imply anything, mind, I'm just asking."

Cassandra reacts oddly to things he says and does so maybe what needs to happen is that he explains all his comments and tries not to make use any more Americanisms. Maybe if he treats this like talking to someone who's just learning English (another comparison he's not going to mention to her).