The only things you can do now are to arrive at court in plenty of time, dressed smartly. Talk to your solicitor as much as possible before you are called, and ask as many questions as you like, it may help to put your mind at rest.
Above all remain calm. Do not react to the other girl's testimony by shaking your head or protesting, laughing, etc, no matter how ridiculous it sounds to you. Answer all questions truthfully, remembering to speak clearly and be polite at all times. Try your best to remain calm during cross examination, dont let the solicitor from the CPS provoke a reaction out of you.