Thnaks Christie! I love that exchange. It'a a detail than one can easily miss at first viewing, because we are momentarily concerned with what Aguirre is saying over the phone.
Yeah, that's how I feel about this scene, its one that we dont really take too much notice of in the big scheme of things..but those furtive glances are indications that, as alicia so perfectly put it, the seeds of attraction are being planted....

(by the way, I love Ennis's hair in this scene! So cute.