I don't watch a lot of horror, but Drag Me To Hell made me realise you can enjoy like you might a rollercoaster (albeit a rollercoaster that goes 'quiet ... quiet ... HANDKERCHIEF ATTACK !!!)
She has an eating disorder. Notice that everything bad she experiences has to do with food or her mouth? Also, she's very thin and has symptoms of anorexia like nose bleeds and her hair falling out. There are some scenes, like in the bank, where everyone should be freaking out, but they're only looking at her. She's hallucinating.
More here:
https://www.cracked.com/article_18967_6-famous-movies-with-mind-blowing-hidden-meanings.html