It should have been you / Lynn Slaughter.

Seventeen-year-old Clara is just starting to recover from her piano prodigy twin's unsolved murder, for which she herself was a suspect. Her lifeline has become the advice column she writes for her high school newspaper. But then threatening e-mails begin arriving in her staff inbox. Convinced that her e-mail stalker blames her for her sister's death and is out for revenge, Clara undertakes her own investigation. But as she draws closer to the truth about her sister's life, she puts her own in grave danger. In the meantime, she falls hard for Ben, a new boy in school, who turns out to have a secret of his own. She also tries to help a reader involved in an abusive relationship, only to find herself a little too involved for her own good.