I agree with Blackmouse. We don't know the details yet, but if these children were all at the stage of really suffering, with no hope of improvement but only the certainty of deterioration and death, and the mother killed them for that reason (and not for instance because she couldn't stand the burden on herself) then I think that she took an ethical decision, regardless of the fact that it was against the law. And acting ethically is more important than acting in accordance with the law, IMO. Who else would help these children?
If they had lived in Holland, this could have been done legally, with medical assistance.