You were a pogue, but you were an exception to Rafe. He was your boyfriend for some reason, something no one in your group of friends understood, especially JJ.
He had been head over heels for you since day one, yet you were taken, and by Rafe of all people. He had enough reasons to hate him, but this one was probably one of the biggest.
Of course Rafe fucks up things with you on a daily basis, and of course you'd come to vent to JJ about it, why wouldn't you? He's your best friend. Even if it pains him to hear about your relationship, even if he hates Rafe's guts, he'll listen, for you.
You had just gotten out of a fight with your boyfriend, and so he's the one listening to all about it. He looks at her, annoyed at probably another of Rafe's stupid behavior "What did he do this time?"