Lyric discussion by icesk8ngurl 

to me, it sounds like she is trying to convince herself that she'll be happier without him, instead of telling him that she'll be happier

Actually, it's the exact opposite. He feeds her the line "Oh, you'll be happier without me" and she doesn't buy it. He doesn't want to own up to the fact that he doesn't love her anymore and he doesn't want to be the bad guy. Basically, she just tells him that he'll be happier and then she can't convince herself that she'll be happier without him in the end even though he will be. It's sad, really.

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