Anyone that believes "we should believe women that report a sexual attack" should agree that this woman should face a very harsh penalty. If the penalty for making false accusations is not harsh enough, we can't have a society that trusts these kinds of accusations.
(Some) rapes are very hard to prove, since the difference between consensual sex and rape is often "he said, she said". In the cases where they are disproved "note that not-proved is not the same as disproved", the accuser should be appropriately punished.