Sacoolas, 45, was driving on the wrong side of the road when she crashed her Volvo and killed the 19-year-old motorcyclist in August 2019.
In December 2019, the Crown Prosecution Service authorised Northamptonshire Police to charge her with causing Dunn’s death by dangerous driving.
On Thursday, she attended the Old Bailey by video link from Washington DC and pleaded guilty to the lesser offence of causing Dunn’s death by careless driving in August 2019.
Adjourning sentencing until next month, Mrs Justice Bobbie Cheema-Grubb told Sacoolas that although she could not compel her to face justice in person, it would provide “weighty evidence” of “genuine remorse”.
Outside court, Dunn’s mother Charlotte Charles said that “of course” she wants Sacoolas to return to the UK to be sentenced.
“I do very much hope that she listens to the judge’s words and makes the effort to come back because that will truly show us all how remorseful she is," Ms Charles told the PA news agency.
“It’s all well and good saying you’re sorry but demonstrating you are is another matter.”
Harry’s father, Tim Dunn, said: “Anne will do what Anne will do — it’s up to her what she does.
“But I would urge her on behalf of my entire family to do the right thing and come back for the sentencing hearing.”
About 20 members of Dunn’s family, who have long campaigned for his killer to face justice, were sitting in court.
Ms Charles and Mr Dunn held their heads in their hands as Sacoolas pleaded guilty.
Prosecutor Duncan Atkinson, KC, said the plea was accepted by the Crown after consultation with Dunn’s family and consideration at the “highest level”.
Mr Atkinson recognised that driving on the wrong side of the road put at risk a vulnerable road user such as a motorcyclist and was capable of amounting to dangerous driving.
But the fact that the offender was “an overseas national without experience of driving on the roads of this country” was a factor in considering her culpability.
“The prosecution has taken account of that and of the mitigation available to this defendant and the balance of the interests of justice," Mr Atkinson said.
“The plea that has been entered was one indicated at magistrates’ court and indicated indeed before that as being offered by the defendant.
“It has been considered at the very highest level and with the very greatest care, and with close consultation with Harry’s family.”
He said the Crown would not be proceeding to trial on the causing death by dangerous driving charge.
Ms Cheema-Grubb urged Sacoolas to travel to the UK to be sentenced in person, but admitted she had no power to force her.
She said the offence of causing death by careless driving carried a maximum sentence of five years imprisonment, with options from a medium-level community order to three years in custody.
Ms Cheema-Grubb explained the reason for the unusual way in which the hearing was conducted, by video from overseas.
“The fact that the defendant could not be compelled to attend court in person means there was no other way to obtain her plea to the charges," she said.
“It was in the interests of justice in the particular circumstances of this case to grant a live link for this hearing.
“That is no reason in itself to grant a live link for sentence. Although I have not yet decided what sentence to impose, I very much have in mind the submissions as to the sentencings.
“Ms Sacoolas is a convicted offender and a consideration of the interests of justice now must include the ability to enforce any sentence or any ancillary order I impose.
“It is agreed any sentence I impose is likely to be unenforceable while the defendant remains outside the UK. I have to consider the reason why the defendant does not attend court in person.
"Alongside an early guilty plea, one of the most powerful mitigating factors in cases of death by driving is the degree of remorse felt by the defendant.
“Attention has been rightly drawn to the remorse by Ms Sacoolas in co-operating with these proceedings at all.
“Despite her conviction today, there is no order I can make to compel her at the Central Criminal Court for sentence.
“I direct Ms Sacoolas attend court to be sentenced. If the sentence … is one that does not involve immediate custody, there is to be no barrier to her returning home after the hearing.”
The judge reminded the court that the case concerned the “sudden and unexpected” death of a young man three years ago.
“Attendance would provide weighty evidence indeed of genuine remorse,” Ms Cheema-Grubb said.
The defendant acknowledged that she understood after the judge also imposed an interim driving ban and ordered a pre-sentence report to be prepared.
Sacoolas, who wore a white blouse with her dark hair tied back, appeared composed throughout the hearing.
She only briefly appeared to be flustered when she mistakenly entered a not guilty plea to the lesser charge before quickly correcting herself.
Sentencing will be fixed at the Old Bailey in the week of November 28.