There is only one way to enforce the law, which is to enforce it upon learning of all the circumstances, both in favour and not in favour of the accused. The fact that you are not familiar with the law never protects you by design ("oh sorry, I never realised I wasn't allowed to just take their bike and ride away") — so it's upon the courts to make judgement on the entire set of circumstances.

The problem with any immigration service in the world is that they are dealing with non-citizens which lack most protections citizenship would have given them — which means that it may take its sweet time before courts actually hear her defense and probably decide as you suggest (along with introducing a 3 or 5 year ban on entering the US).