You first need to hire an attorney and have him/her consult with the prosecution as soon as possible. Catching the case before it is filed by the state attorney's office is the first and foremost way to defend yourself against any type of accusation. Also, investigate her prior history, any prior accusations by her of battery, rape, etc.etc. in the court file, she if there is a history of accusations there. Also look for reasons she would be biased towards you, owing money, prior girlfriend of yours, has it out for you for some reason, etc.etc. That's how I would start, but start now.
You need to speak to an experienced reputable criminal defense attorney in the county where you are being prosecuted. If you cannot afford an attorney, you need to request a public defender when you get to court. Only an experienced criminal defense lawyer can review the facts of your case and help you prepare a defense.