Cheap trick with super hot retarded girl-character. But works for me!

And sometimes it isn't...

What's this 'trick' you speak of?

We've met before, haven't we?

I don't know if it's is a trick, but it is definitely a very cheesy and annoying cliche. An uppity and naive female character which somehow appears edgy and changes a male main character.
What's worse is in this film it is clearly done on purpose.

She was the primary source of pathos and the instant you saw her you had to think "my god, how could that person possibly be alive?" and from then on you are worried about her. She definitely kept me interested in the movie if not simply to see if the kid would have sex with her.

I was aroused by her dumbness