whats that movie called about a boy and a girl and they fall in love at a very young age... but...

the girl kills him at the end on the beach with a pillow or something because he gets over protective, and they lived next door to eaachother so they made a hole in the wall and used to hold hands when they fell asleep, and there was a big fight in a club and her boyfriend hit another guy that was talkin to her over the head with a ashtray?

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