Early 90s? Shouldn't there be some sort of statute of limitations on these types of accusations? Anybody can make such accusations, but it's difficult to defend oneself especially when they supposedly happened a quarter century ago.
And for Underseer's information: no, 15 (almost 16) is most definitely not "pedophilia".
The time frame is problematic: it's a long time between the alleged assaults and present. Getting reliable evidence of any kind will be difficult, making legal charges unlikely.
That said, it would have also been extremely problematic at the time to bring charges forward and to have an actual police investigation. Partly, it is because times may have changed ever so slightly to make it easier now (but only incrementally so) but largely it would be difficult to get a local police department to file statutory rape charges against...a police officer of any kind. Now or then.
Then it brings up motivation for coming forward now, after so many years. There are a couple of reasons why this might be coming up now.
First of all, it is really difficult to actually process the fact that you've been sexually assaulted, to admit what it was, to admit that you couldn't get out of it/fight him off/avoid being in that situation in the first place. It's much easier to tell yourself that maybe you really did want it, that an adult who was twice your age surely knew better than you did what you want. It is hard to describe exactly how much girls are raised to discount their feelings, but it's pretty powerful. It can take a long, long time to fully realize what happened and also a long time to have the courage to come forward. Trust me, she knows how much she will be disbelieved by many, many people.
Secondly, this person may well have a daughter or a niece who is about the same age. Sometimes, that is enough to re-awaken a lot of memories, consciously or not, and for almost all parents, one begins to have a different kind of protective feeling for one's daughter. And if you've been assaulted yourself, multiply that by a large number.
Finally, is there a reason to believe that the police officer who assaulted her in the 90's might still be at it? Might suddenly have access to a vulnerable teenage girl? That can be a pretty powerful motivating factor: the desire to protect someone from what you went through.