With the existing facts as we know them, I believe you can state that with 99% certainty they are blameless. Unless the Border Patrol intentially withheld food or water from the little girl, which is highly unlikely A pre-existing condition of which even her father was apparently unaware, killed the child.
All evidence points to the fact that the Border Patrol did everything by the book and when the little girls distress became apparent, everything in their power to save her.
At this point with all the facts as they exist, their is very little doubt and certainly no reasonable doubt that they acted appropriately.
Merry Christmas