Hi, I'm Heather, an attorney with 15 years experience and I'd like to assist for informational and educational purposes.
It's likely that if she went to the police, that they would have contacted you for interview. They haven't, and that tends to make me think that she has not filed a report. However, it's not determinative.
You can probably get a copy of the police report, if there is on by filing a request for public records. Since you would be the subject of the record, you can request it. You can request the records by going to this website, where you can find the form and instructions: http://mdsp.maryland.gov/Pages/PublicInformationRequest.aspx
Without filing a court case, you cannot issue a subpoena, as subpoenas are used to obtain documents for pending court cases.
If she has told people that you've raped her, then there is a potential defamation case; however, her defense to that will be that she was telling the truth, as truth is a defense to defamation. If you sued her, the civil defamation court (not criminal court) would have to have a trial on whether you committed the rape, inside of the trial about whether she made the defamatory statements, in order to assess her defense that she was only telling the truth. For practical purposes, most people don't end up filing defamation cases like that, since they are very expensive.
Have I been helpful tonight? Please let me know if I've answered your question?