I'm glad I don't have to judge. This is a no-win situation although Helen is obviously already the loser. But that can't be reversed so it seems in my unprofessional opinion, that Claire needs psychiatric help and that route would be the best for her future. Prison would be harsh and not help her in any way. And, as you said, she will always live with the knowledge she killed her own sister who was really so innocent under the circumstances of her disabilities.