The Vienna Convention brought about the concept/laws of Diplomatic Immunity - which was not meant to give protection, in cases like this.
Essentially/seemingly - a civil case, where a middle-aged bored housewife (in this country for 2/3 weeks) doesn't bother acclimatising to local laws.
Then lies about her future whereabouts, disappears, is supported (hidden?) by US authorities - and expects everyone to forget the tragic and fatal incident.
Remorse - none! Regret or condolences either. Even though this confident and uncaring lady had been cited for traffic violations in Virginia before.
It's no secret that US military bases - here and elsewhere in Europe (albeit an economic benefit to the local community) - seem impervious to relevant legislations.
Many use the $ on base, ridicule the backward limies (we make their aircraft/weapons) and expect eternal gratitude for help in WWII.