Hotaru spoke the truth. But still, teenagers, especially girls in a conservative society like Japanese, are not well informed on what to do, or even if they are, are not taken seriously by authorities. Now, if only there are someone, preferably adults, they can confide in...
Of course, being a manga, the cops' reactions might or might not be exaggerated. Maybe they have police officers who are just as competent as the ones we see in Detective Conan.