There are many legitimate reasons why people may not immediately report to the police. It may take time to process what has happened to them.I don't know man, she should just go to the police like any sane person would.
There are often deep feelings of shame or guilt associated with it. The initial response may be to avoid reliving the experience and carry on with their everyday lives. This is a self-protection mechanism following serious trauma.
Do you have any idea how high the percentage is for people not reporting to the police?
It isn't always as easy as you think.