20-year old women aren't always that smart or mature. I'm going to say the Rexburg police may have made the right call in this instance, although I'm not certain.
It could have been some false information was funneled to the victim prior to the incident, which would nullify his claim, but she may have come to realize her culpability in it by being gullible and inexperienced.
Cops make calls that are unseemly for a reason. If their call settles the incident, it's certainly cheaper than forcing taxpayers to house Miss Not-too-smart for 10 years for lying if he lied to her too.
I hope she gets counseling. And I hope he gets counseling if he thinks he has to exaggerate his honorable intentions to procure instant satisfaction.