My interpretation(Spoile rs)

I found I liked this movie unlike a lot of thriller's/horrors out their in this age.

The girl is not evil, just awkward but turned vengeful. She was sickly and small along with being raised in an orphanage. Her only friend was Sandy. She showed Sandy the game, but sandy played it with other's in front of the orphanage without inviting her. Of course she would freak. Most people freak when their friends decide to leave them out of a group thing and Sandy WAS her only friend.

Remember when she was killing of everyone? She made everyone forget they existed because everyone forgot about her. Sandy being directly her friend was due a different punishment by letting only her remember those forgotten. Also they had dressed up as zombies to scare the frail girl at her own game. Sandy could have very well have said no and done the right thing but she wanted the boy, and like most girls crushing after the guy they will go along with anything hoping he would like them.

The girl used the zombie ploy used by the kids to scare her unto them. Seizures are a very serious thing. My friend has epilepsy and sometimes I witness this and can she he is struggling to breathe. Not to mention the girl had asthma and was scared into a coma. Her best friend and her savior in her eyes had been turned into a zombie and had come after her. When they witnessed her having a seizure they did nothing but run. They chose to forget they caused it because they didn't want to get in trouble, like most kids would do.

If you chose not to see the story and meaning it's quite fine. I prefer to address and dissect plot's given to me by the movie.