This line, particularly:
"And no one else can break my heart like you."
Because yes, eventhough Vi may appear cool or unaffected to whatever jerkiness Ryn does to her, me, as a reader, feels how hurtful it must be for Violet to have her bestfriend do something like throw her mothers necklace into no man's land. Not to mention the author's mad gut-punching writing skills that would suck you right into the characters head.
I love both the music and lyrics. And the video as well. This song makes me see past the annoying-ness of those few love and hate relationships I've mentioned above. I'm not saying that I hate all of them and that it also applies in real life situations (only the ones in books). It's just that sometimes it gets to the point of ridiculous, if you know what I mean.