While I was watching the movie, I thought the same thing about her putting herself in danger over and over. But I think it's important not to judge Cassie by our own standards of reasonable. The scene with the character played by Molly Shannon made the extent of her damage clear. In a way, she was playing Russian roulette. If her actions were strictly about revenge and getting justice, she would have taken the video straight to the authorities rather than planning that final sex heist. In the end, she had to sacrifice herself to finally get justice. Unfortunately, it wasn't justice for her friend but justice for herself.