Sounds great in theory, but what criteria do you use to decide who the law applies to, and do you have the manpower to enforce a more complex set of rules?
Simple: you allow the judge to use their discretion. They already do, anyway. If a child has more than 10 unexcused absences, they can be taken into court, and the judge can then decide, in the circumstances, whether a child deserves a talking to, community service, jail time, etc.
Not really an excuse. There are other ways to support siblings, such as child protective services and crap like that. It's her job to go to school. She doesn't go, she can face the consequences, why make an exception?
You realise that state child protection is horrible, right? The siblings would probably be separated, they'll be introduced to all sorts of problem influences, and the net result will probably be that they'll be worse off than they currently are. Frankly, there's no way you can fault the girl for wanting to keep herself and her siblings out of that system.
If you disagree with a law you work on getting it changed, until then it's your duty to follow it or you'll face the consequences.
Except in this case the person in question happens to be a child, with basically no resources or time to try to change the law, and probably with plenty of other problems on her plate.
It seems to me that there's something wrong with a legal system that doesn't take these kinds of exceptional circumstances into account. Exceptions already exist for murder, fraud, theft, etc.
This is the problem with these kinds of under-the-radar laws -- they're not given enough thought, because the people they affect (children, or homeless people, or ...) don't matter.
Insofar as you could not effectively argue in her legal favor, you are right. But this isn't just a legal issue, it's a political one, and it's worthy of discussion.
Erm, let's not go that far, because the thread will get locked.
As a discussion of education, family, and the law, this is kind of interesting. Let's try to keep politics out of it, though.