@Raivu: Well if you have had no relationship with her at all, it was shown that she asked you out and you denied her advances, your friends know the kind of guy that you are, and there is no proof of sexual intercourse, you can't really get into trouble.
Her entire case would be hear-say and any evidence would be circumstantial at the very best. And if she says she has a condom with your fluid in it, that is easily solved since your DNA wouldnt match that DNA, and if at any time she states that she has evidence, then pull the "pics or it didnt happen" card. Cops cant take only her word and not believe you, that is retarded, because she is a 14 year old in high school, more often than not, she is lying. Bust her on it.
And second of all, if you were her first time, then she should be able to tell intimate details about you and your body, and that is obviously easily provable to the negative, but in your favor.
Lets face it, liars dont think about it this deeply, and that is why liars get caught. And trust me she will get caught in her lie. Eventually.
Actually, we learned this just last year in Human Sexuality class. Sexual assault is the only law (or one of only two laws) where you're guilty until proven innocent.
Sucks. Just hope she doesn't take it to court or you're fucked.
Unfortunately GAMEChief is right. you will always be assumed as guilty, very rarely is the accused believed to be innocent off the back.