You prepare by advising your attorney regarding the specific facts. Discuss cross examination to catch her lies. If that does not work, you may have to testify. However without details I cannot advise and recommend you speak with the attorney defending you at trial.
The answer above is only based upon the limited information provided. The answer is limited and my review is likewise limited, and thus the response is not intended to be acted upon as legal advice. Although licensed in numerous states, I am currently only licensed to practice law in the state of Nevada. No attorney-client relationship is formed until you sign an attorney-client agreement with my office. Any information provided is for discussion purposes only and there is no attorney-client relationship formed. Only general legal information is provided. Each case is unique and accurate legal advise would require review of all details and documents for each specific case. It is possible that the comments here, while meant to be helpful, may in some cases not be complete or accurate.
From the information you provided, it appears clear that you need an attorney. These charges are extremely serious and can affect you for the rest of your life. You need to write down a timeline making sure to leave nothing out from the time you got there to the time that you found out about the charges. Defense to these type of matters is not easy, especially considering the liberal nature the the law is applied.
We handle a large number of BDV, you are welcome to contact my office, but either way you do need an attorney to guide you through and represent you in this process.
This "answer" is not intended as legal advice and does not in any way create an attorney client relationship.