This turned out to be far more interesting, even thrilling, than expected.
One of my huge turn-offs in mysteries, thrillers (and horror movies), is protagonists who do stupid things just to further the plot. Why do they put themselves in danger, rather than just calling the police? But here, it all makes sense. Our hero is a high-school student, isolated even more than your average teenager by the need to care for her mother, who has Multiple Sclerosis. Every time I thought, "why would you do something so boneheaded?", I'd think back to my own (much easier) adolescence, and remember that (a) I did some pretty stupid things; and (b) I would never have dreamed of asking an adult for help to get out of the inevitable consequences!
Ultimately, this story is all about how children become adults, learn that they need to form relationships (of many kinds — Janus forms deeper bonds with her mother, her mother's boyfriend, boys, and even Authority), and learn to take responsibility.