I like there being no evidence of the crime. What if there was something in her past that made people less likely to believe her? Something that made them think she was making it up? Maybe she had a habit of doing things to get attention when she was younger or something? If no one believed her, that could set the scene for her to figure things out herself and not involve the police. I really hate reading books where there is no earthly reason for the hero/heroine to go after the bad guy themselves without involving police.