First off, this is some of the worst acting I've seen in a long time. Nobody in this movie can act to safe their lives.
It is impossible to root for any of these characters because they're all written as over-the-top teenage stereotypes. All of them are idiotic, promiscuous, assholes, or all three.
The Live-in Nanny is even more confusing. She encourages the kids to play "Charlie, Charlie", and early in the movie is seen reading from a book with a Pentagram on the cover. So you'd think it's clear she's a villain, right? No. She claims she's trying to help them, and then one of the girls just shoots her towards the end.
Not even all of the sins are shown, and there are seven unlikable teens the movie expects us to care about. We see Lust, Envy, Wrath, Sloth, and Gluttony, and they just reuse sins. We don't really see Pride or Greed.
Longstory short, most of these assholes die except for the blonde girl and the Asian dorky guy because he was high and went out to get food. He shows up at the end and gets her out of the house, then turns back to the camera with red eyes to show us that he's possessed.