If a child was killed in a car accident where the driver did not own the car but the owner's daughter was a passenger who is responsible?

First of all sorry to hear of the child's death .

Secondly get a lawyer

If the driver was not the owner it would depend on the facts related in the accident . For example if the driver was not authorized to take the car or was speeding/drunk etc the driver would definitely be At Fault . The owners daughter being a passenger should have nothing to do with who is responsible for the accident unless she contibuted to it .

good luck