Probably nothing new. But: the Thing that always gets me about the ending of Jennifer's Body ? How the instant that Needy tears off Jennifer's BFF necklace (also heart-shaped) she just... collapses. I always read that as the real moment Jennifer died (again). After all, heartbreak is also a kind of stabbing, no? Once possessed, Jennifer only ever acted human for Needy. Now Needy doesn't want her anymore. Then Needy names the source of her downfall. "My tit." "No. Your heart."
And only THEN does Needy realizes that she's lost too. Because she was in love with Jennifer! She was in denial (of her feelings / Jennifer's monstrosity) for as long as she could (I think she pushed it down again as soon as she tells Jennifer maybe you really did die). But now she has nothing but time to think, and has Jennifer's last gift (diet demon powers) and all this rage and feeling to work through. Why did she do it? Because Jennifer was wrong. Yes. But also because she loved her. Why does Needy murder the band? Because she loved Jennifer.