Well she was 11 at the time of this lie. I know that most 11 year olds don't think of what exactly will happen when they end up lying. Who knows, she may have even been coerced into saying that she was raped.
Its a pretty messed up story, but I honestly don't know what to do about it. I can see why people want to have her charged with some crime, but I also see why the DA doesn't want to charge her.