I Have Touble Finding A Book

[Ars10001]

Help me please dear book community!
I´m having a hard time finding a book that I read several years ago. I don´t know the author or the title, but I do remember the plot.

The story is about a woman who witnessed her little sister be raped and murdered after a party which she brought her to. While she was grinding on her boyfriend, unknowingly, her little sister was getting drunk and drugged in a car with some strangers.
She goes about with her life and If I remember correctly her family kinda blames her sisters murder on her, and she feels angry, but also remorseful. I specifically remember the book constantly switching between past, present and future.
She is confronted in the end of the book by a girl she had concidered a friend. It turns out this girl´s brother was convicted for the rape of her sister and the "friend" is angry about it and tries killing her, ending in her accidentally being killed (by herself or the main characters boyfriend, can´t remember the details)

PLEASE HELP!

[woofgang]

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