The charge will not necessarily get dropped. She will not necessarily get in trouble for lying. We need much more information to give an answer here. Just because there' no physical evidence from an examination, doesn't mean there is not other evidence. Depending on the strength of other evidence, the solicitor's office might believe they can prove the elements of the charge and would not drop it. If there's zero other evidence of the crime, and the determination is made that she did make a false report to police, she could be charged.
Criminal charges are formal accusations in court that someone has committed a crime. Criminal charges have many classifications and degrees of severity.