| Quote #4 If they dance any closer together, they won't have to go off in a corner to have sex. (12.64) |
Here's our take: Clary probably wouldn't have cared if Simon were dancing with anyone else but Isabelle.
| Quote #5 "Let's not be hasty." Jace was actually grinning, the bastard. […] "[Simon's] cute like that. Look at his little pink nose." (13.115) |
Even the third-person narrator thinks Jace is being a "bastard" for teasing Simon. And when the narrator thinks you're a jerk, well then you know you're on thin ice.
| Quote #6 "You'd be happy to leave him if it weren't for her," Isabelle said, managing to inject the single syllable word with enough venom to poison an elephant. (13.119) |
By italicizing the pronoun there, we know that Isabelle really doesn't like Clary. So it looks like jealousy is a two-way street.