Yes, the State Department deserves some blame for South Sudan's continued use of child soldiers. The United States could at least express displeasure, if not enforce sanctions, over the use of the deplorable act of using child soldiers, which is a major human rights violation. Hillary Clinton, as leader of the State Department at the time, in not using her power to exert any pressure on South Sudan, now has some responsibility over the continued use of child soldiers in that country.
Yes, as the secretary of state at the time, Hillary Clinton is to blame for the State Department giving South Sudan a pass for its use of child soldiers. Although it was in her power to do this, it was not within her right, as the use of child soldiers is unacceptable and the American people shall not accept their officials abusing their power in this manner.
She is to blame. This is because Hillary has a powerful position as Secretary of State. She could have used that power to protect the children but instead she went to the dark side and sided with the government. Although there are probably intricacies that only Washington can understand, allowing child soldiers seems quite evil.
When one is in a high level government position such as the Secretary of State as was the case with Hillary Clinton, it is impossible to know exactly what information they have on each particular case. By blinding judging the decision of the Secretary is essentially playing politics with real life matters.