There is nothing to debate. Call the police and social services to protect the child and potentially other children.
For everyone who advocates this, they would be willing do this against the wishes of the victim?
The victim may be now an adult, be married with kids and not want to get involved. She may not have even told those close to her, yet you would still go running to the police knowing the potential upset it may cause. The correct answer in this case is no you wouldn't - it is and should be entirely up to the victim.