Well, without more details, it's hard to tell the exact story. However, generally speaking, a 16 - year - old becoming a killer might be the result of a complex combination of factors. It could start with some form of abuse or neglect at home, which leads to psychological problems. And then, being influenced by the wrong crowd or having easy access to weapons can push them over the edge.
I'm not sure which specific 15 - year - old killer girl story you are referring to. There could be many fictional or real - life accounts that might fit this description. Maybe it's from a particular book, movie or a real - world crime case that has been sensationalized.
Mental health issues might be a factor. A 16 - year - old with undiagnosed depression or anger management problems could be more likely to commit violent acts. Also, being influenced by violent media or a bad group of friends can play a role.
I'm not sure which specific '15 year old killer girl story' you are referring to. There could be various fictional or real - life accounts. Maybe it's from a particular book, movie or a news event. Without more context, it's difficult to tell the exact story.
One possible motive could be revenge. If she has been wronged or bullied severely, she might feel that killing is the only way to get back at those who have hurt her.
Another motive could be coercion. Maybe she was part of a gang or some sort of criminal group that forced her to kill. They could have threatened her or her family if she didn't comply. Or perhaps she was in a situation where she thought killing was the only way to protect someone she cared about. For example, if she was in a war - torn area or a place full of violence, and she believed that by killing a particular person, she could save her friends or family from harm.
As a fan of online literature, I can't judge whether a physical book is suitable for a 12-year-old. This involved copyright and publishing regulations, which needed to be decided by the specific publishing party and the education department. In addition, everyone's reading preferences and cultural background are different, so it's best to understand its publishing background and cultural background before considering reading any physical book, as well as whether your reading interest and reading ability are suitable for it.