She seems to be reading a parody of Yamikin (Loan Shark) Ushijima-kun, which is certainly something you shouldn't be letting kids her age read.
The themes are, beyond the adult content (like a gang rape and murder), is just sort of plain dark (if entertaining, in the way a dark movie is) and full of horrendous scumbags (including each member of the main cast, more or less) preying on even worse specimens of humanity. It's a really good read though, if you're into drama and crime stories.