It's a civil matter and the standard of proof is much lower than if it were criminal so I wouldn't say it will not be proven if it goes to court.
It's well known that victims of sexual assault, where the parties know each other, often do not report these things right away. In many such cases the victims do not even report the incident and continue to see the perpetrator socially. See R. v. Ghomeshi, a trial which was just completed in Toronto. You can find the media reports if you Google it.