This person has been co-operating with the police. They've just fled to America. If they hadn't fled, they had pulled out of an American airbase and momentarily driven on the wrong side of the road, tragically caused the death of this young lad. The judge in those circumstances would be incredibly lenient, the charge would be causing death by careless or inconsiderate driving. https://www.sentencingcouncil.org.uk/offences/magistrates-court/item/causing-death-by-careless-or-inconsiderate-driving/

Causing death by dangerous driving, they would have to be more to it than a momentary lap of concentration, excessive speeding, drinking, deliberate dangerous driving. The fleeing part is the worst, I could imagine a suspended sentence, if the circumstances were truly just exiting a base and forgetting the correct side of the road. If she was overtaking someone and caused this accident it would be more deliberate for example.