Then why do you use a conditional there? I am pretty sure for her to face (legal) consequences, a courtcase would have to show that those were actual fake allegations, so it counts as libel. Just not being able to prove the correctness of her allegations is inssuficient. However, the problem I pointed towards is indeed a major reason public Twitter accusations are very problematic. People accused this way but not in a court have no good way to defend themselves and face the same societal consequences as if they were ruled guilty in court without any chance of a closure, unless they feel really confident about being able to prove their innocence in a libel courtcase.
No, it cannot work like that. If failing to prove rape allegations was sufficient to judge them as libel, reporting any crime, especially rape, would be hell.