Feng Tiansi was actually a smart person; in adversity, this twisted kind of ability in her was forced out.
She was underage, and with that video she submitted proving that the poison was brought in by Lin Meina, plus no third person was present. As long as she stuck to the story that Lin Meina accidentally killed herself, even though she was suspicious, the police still couldn't convict her.
She calmly told the police how it all happened.
Lin Meina asked Bo Chong'er out over the weekend and forced her to poison Bo Chong'er. She refused, so Lin Meina hit her.
Lin Meina lied that the poison wouldn't be fatal, it would only make someone lose face. She didn't believe it and made Lin Meina take a sip to show her. In order to coax her into agreeing to harm Bo Chong'er, Lin Meina drank a mouthful. Back then Lin Meina probably meant to spit it out, but just as she did, Feng Tiansi bumped into her, and without noticing, she swallowed it.
