So, you let the daughter die in the road.
THEN tell the father afterwaords.
No smart*** But if you are worried about panicing parents interfering with the care of the injured person, maybe you stabilize the patient and then call the parent when the ambulance is on the way to the hospital.
That's another issue and not my call to make. However, if you do call the father and indicate that his daughter is dying, don't act shocked when he tries to get to his daughter.
Using your logic, you would call the parent to let them know the child was dying, but then tell them they are going to have to stand behind the yellow line when they got there.