Young women are creative, but we have to work with what the culture gives us. When there were no female rock stars or rappers, we latched on to the men who were maybe doing what we wished we could do. Girls who are troubled and alienated have no real female role models to choose from (save a couple of poets who killed themselves decades ago) but plenty of angry men committing atrocious acts, and the number seems to multiply each day.
Except if you were in 8th grade in '99 you had Madonna, Joan Jett, Cyndi Lauper, Chrissie Hynde, Siouxsie Sioux, Patti Smith, Janis Joplin, Queen Latifah, Nina Simone, Grace Slick... I mean, I could go on but why bother?
Girls who are into Harris and Klebold probably have parents who were into Charles Manson.
It's this dumb counterculture thing that gave GG Allin a career. Prior to Tumblr, of course, you had to express these things in meatspace which kept a bit of a lid on it and definitely curbed the fanfic but there's a real disapproval-baiting amongst ill-adjusted adolescents.
And half this site dated those girls at one point or another.