Diplomatic immunity
Suspect Anne Sacoolas agreed to a resolution with Dunn's family in the civil case.
Sacoolas, who returned to the US after being charged with death by dangerous driving, said she would be willing to meet with Dunn's family.
PC Harpers mother asked Anne Sacoolas if she could "begin to imagine if what happened to Andrew and Harry had happened to one of your children?"
The 19-year-old’s family are set for a two-day judicial review hearing at the High Court in November where they allege the foreign secretary “obstructed justice”.
Anne Sacoolas returned to the US after the 19-year-old's death last year.
A spokesman for the teenager's family called it a "monumentally large step in the right direction”.
A spokesperson for the family also said they were taking claims made by the Trump administration "with a pinch of salt".
The 42-year-old, who is married to a US intelligence officer, is accused of driving the car that hit and killed the Northamptonshire teenager.
UK police have questioned Anne Sacoolas over the accidental death of 19-year-old Harry Dunn and passed on details to the Crown Prosecution Service. The UK government are currently reviewing the rules which govern diplomatic immunity arrangements, which Sacoolas originally used to flee the UK.
Anne Sacoolas has asked to be interviewed by officers from Northamptonshire Police.