First of all, can we stop calling these people "migrants?" They are "hostile invaders" trying to enter this country illegally,
Secondly, the child was already exhibiting symptoms before she got here. It's possible she was sick before she and her father left home on this journey. If he was a responsible parent, he would have given up on this invasion and obtained help for his daughter.
I'm sorry this child is dead, but I do not believe anyone in this country is to blame for her death. Maybe if her father had not been so greedy for whatever compensation he was getting to make this trip and for whatever free stuff he thought he would get if he was allowed entry into the US -- maybe he would have put his daughter first and she would be alive today.