Jace's allusion to Alice in Wonderland proves that Shadowhunters do read books by mundie authors (assuming that Lewis Carroll was actually a mundie), and that he's about to lead Clary into a world that is both similar to her own and radically different.

Alec is to Jace what Simon is to Clary. The object of their affection loves them, but only in a familial way.

Clary's pretty insecure. We have a feeling that if the girls weren't cute, Clary either wouldn't think they were laughing at her, or wouldn't care.