The heartbroken mother of a British teen killed in a car crash with the wife of an American diplomat issued an emotional plea Monday for the driver to return to the United Kingdom and face justice.

?We?re all broken,? Charlotte Charles told Sky News, her voice choked with grief. ?We?re just utterly shocked and appalled that somebody is allowed to get on a plane and go home and avoid our justice system.?

Anne Sacoolas, the wife of US diplomat Jonathan Sacoolas, was driving on the wrong side of a Northamptonshire road in August when she allegedly struck and killed Charles? son, 19-year-old motorcyclist Harry Dunn, head-on, officials have said.

Sacoolas, 42, initially cooperated with local authorities, but eventually invoked diplomatic immunity and left the UK with her husband and their children ? reportedly at the suggestion of lawyers and US Embassy officials.

?All we need to do is meet her,? said Charles on Monday. ?All we need to do is ask her to come back. It?s not much to ask. She?s left a family in complete ruin.

?We?re not coping,? she added. ?We?re literally just getting through hour to hour every day, going with the flow of what we need to do. ? We just have to keep going to try to get some closure.?

Meanwhile on Monday, UK Prime Minister Boris Johnson urged Sacoolas to return to Britain and face justice ? and said that he would directly lobby President Trump if she refused.

Charles offered an emotional appeal to Sacoolas, mother to mother.

?She?s got to be suffering as well. She?s a mom,? said Charles. ?Without knowing who this person is properly, we can?t ? start our grieving process.?