The American diplomat's wife got immunity after the accident that killed the teenager Harry Dunn is "devastated by the tragic accident," said his lawyer.
The legal representative of Anne Sacoolas, Amy Jeffress, said that she "would continue to cooperate with the investigation".
Ms. Sacoolas, 42, went to the United States with diplomatic immunity while she was suspected of crashing 19-year-old Dunn in Northamptonshire on 27 August.
But the Foreign Office said that, when she returned home, she was no longer immune.
A statement in the name of Ms. Sacoolas, whose husband worked at RAF Croughton in Northamptonshire, said: "Anne is devastated by this tragic accident.
"No loss compares to the death of a child and Anne expresses her deepest sympathy to the family of Harry Dunn."
She added that she had "fully cooperated with the police".
"She spoke with the authorities at the scene of the accident and met the Northampton police at her home the next day and she will continue to cooperate with the investigation," the statement said.
"Anne would like to meet with Mr. Dunn's parents to express his deepest condolences and apologies for this tragic accident.
"We have been in contact with family lawyers and can not wait to hear them."
Foreign Secretary Dominic Raab wrote Saturday to Mr. Dunn's family to explain to the British and American governments that Ms. Sacoolas' immunity was now irrelevant.
The letter said: "We have insisted on lifting immunity so that justice can be done … While the United States Government has firmly refused to give this waiver, it is not over.
"We have examined this question very carefully … the British Government is of the opinion that immunity, and therefore any waiver, is no longer relevant in the case of Ms. Sacoolas, as she went home.
"The United States has now informed us that it also considers that immunity is no longer relevant."
In response to this letter, Charlotte Charles, Mr. Dunn's mother, said: "We knew from the beginning that the feeling of" extra "in the abdominal pit was telling us that something was wrong.
"We are proud to have fought for justice for Harry and not to ignore this gnawing in our bodies.
"We would rather have our handsome boy back, but we're also delighted that all these fights for justice for Harry have not been in vain.
"We will continue to fight for a change in the laws on diplomatic immunity and for any other positive change we can achieve."
What is diplomatic immunity?
In the United Kingdom, about 23,000 people enjoy diplomatic immunity, a status reserved for foreign diplomats and their families, as long as they do not have British nationality.
This means that in theory they can not be prosecuted for a crime or a civil case.
However, when crimes are committed, the Foreign Office may ask a foreign government to waive immunity.
Diplomatic immunity is not limited to persons on the diplomatic list. Drivers, cooks and other support staff accredited in Great Britain ("the host State") have the same diplomatic status and immunity.
Earlier, Mr. Dunn's family lawyer, Radd Seiger, had called for anyone to know about Ms. Sacoolas' return to the United States.
Mr. Dunn's parents, who have already indicated that they plan to file a civil suit against Ms. Sacoolas, are expected to travel to the United States on Sunday and travel to New York and Washington DC.
Mr. Seiger said that they "would engage with the media and politicians to get the support of all Americans and ask them to put pressure on the US government to do what they do." 39, it is necessary ".
On Friday, Prime Minister Boris Johnson said that the United States was "absolutely ruthless" in protecting Ms. Sacoolas as a result of the decision to grant her diplomatic immunity.
He added that although President Donald Trump did understand the views of Mr. Dunn's family on the use of diplomatic immunity, the United States was "very reluctant" to allow citizens to be judged abroad.
This followed the revelation that Ms. Sacoolas would not return to the UK when the briefing notes held by Mr. Trump were photographed at a press conference at the White House.
Northamptonshire Police Chief Nick Adderley said the accident investigation would continue.
The force said the video surveillance of the accident in which Mr. Dunn died shows a Volvo driving the wrong side of the road.