The parents are going to be wracked with guilt for the rest of their lives.
My sister lost a son at 9 to cancer; she still beats herself up for not getting other opinions, etc. It has destroyed her marriage and the older brother, who was a straight-A student, is now failing and into drugs.
We need to pray for this family. Such a loss has devastating consequences for years. And they probably never go away.
The little girl is in the arms of Jesus now...
Jesus heals in all ways, brings peace that passes all understanding. Praying for your sister and her family too.