Does Anne Sacoolas have Diplomatic Immunity?

Recent news reports chronicle the fleeing of an American diplomat’s wife from the UK after allegedly striking and killing a British teen. Harry Dunn, the nineteen-year-old British teen, was riding a motor cycle when struck and killed by Anne Sacoolas, who was allegedly driving on the wrong side of the road. Anne Sacoolas’ husband is a US diplomat stationed in Britain. Initially after the aftermath of the crash, the diplomat’s wife agreed to cooperate with any investigation and not leave the country. Subsequent to avowing to stay in the UK, Anne Sacoolas, fled back to the United States and publicly claimed diplomatic immunity from prosecution in the death of Harry Dunn. Does Anne Sacoolas have a valid claim for diplomatic immunity? What should the US do in a case like this?