Causing death by dangerous driving
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?"
A spokesman for the teenager's family called it a "monumentally large step in the right direction”.
He will appear in court on Saturday morning.
Her family said the death "will leave a great hole that can never be filled."
A man and woman, both aged 19, died in a two-car collision on the Lincoln bypass in the early hours of Saturday.
Carol Boardman was hit while riding her bicycle in July last year.
Two people have been arrested on suspicion of causing death by dangerous driving.
Two people have been charged over the deaths.