Anne Sacoolas, the wife of a US intelligence official who was involved in the road collision that killed 19-year-old Harry Dunn, has agreed to meet with his grieving parents and cooperate with a British police inquiry.

But amid continuing questions over her right to diplomatic immunity, it is not clear if she will return to the UK to fulfil a promise to answer police questions about her role in the car crash.

The reversal of position on a meeting appears to have come after lawyers specialising in diplomatic immunity started to advise Dunn’s parents last week, leading them to say they would pursue Sacoolas in the US courts for a civil claim.

Mark Stephens, one of the legal specialists advising the parents, told the Guardian: “The family’s preference now is for a private meeting with Sacoolas to discover what happened and to secure some kind of emotional closure. It must be a meeting without politicians and spin doctors, a personal meeting with psychological counsellors so the Dunn family can find out what happened in the final moments of their son’s life.”

He added that Sacoolas’s son had been in the front seat of her car at the time of the incident, saying “that would have been a traumatic experience for her son, and I’m sure the Sacoolas family are dealing with matters that are tragic as well”.

Facebook Twitter Pinterest Harry Dunn, who died when his motorbike collided with a car outside RAF Croughton, Northamptonshire, on 27 August. Photograph: Family handout/PA

The breakthrough came at the weekend when Sacoolas broke her six-week silence through lawyers to say she was “devastated by the tragic accident”.

Her legal representative, Amy Jeffress, said: “No loss compares to the death of a child and Anne extends her deepest sympathy to Harry Dunn’s family.” Jeffress added in her statement that Sacoolas had “fully cooperated with the police”.

“She spoke with authorities at the scene of the accident and met with the Northampton police at her home the following day. She will continue to cooperate with the investigation,” the statement continued.

“Anne would like to meet with Mr Dunn’s parents so that she can express her deepest sympathies and apologies for this tragic accident.

“We have been in contact with the family’s attorneys and look forward to hearing from them.”

The statement does not include an explicit commitment to return to the UK to meet with UK prosecutors.

In an unexpected letter to the family on Saturday, the foreign secretary, Dominic Raab, said diplomatic immunity no longer applied now that Sacoolas was back in her own country, a formula that allows the British and Americans to reaffirm that immunity did apply when she was in the UK, an issue about which there has been dispute.

He wrote: “We have pressed strongly for a waiver of immunity, so that justice can be done... Whilst the US government has steadfastly declined to give that waiver, that is not the end of the matter.

“The question remains when such an immunity comes to an end, regardless of any waiver. We have looked at this very carefully... the UK government’s position is that immunity, and therefore any question of waiver, is no longer relevant in Mrs Sacoolas’s case, because she has returned home.

He added: “The US have now informed us that they too consider that immunity is no longer pertinent.”

“In these circumstances, Harry’s case is now a matter for the Northants police and the Crown Prosecution Service to take forward.”

Raab, who trained as a lawyer and spent some time working in human rights before joining the Foreign Office in 2000, did not suggest that immunity had ended on Sacoolas’s return to the US when he met Dunn’s parents last Wednesday, and in his letter explained he had not wanted to convey that view to them until he was legally confident.

According to one account, Raab visibly winced when he was told by the parents that they were being advised by Stephens and Geoffrey Robinson QC, the two leading British specialists in diplomatic immunity.

Stephens said that regardless of the status of her claim to immunity in the UK, it was always clear from previous case law that diplomatic immunity did not apply once a diplomat returned to their own country, and that, for instance, a Russian diplomat involved in a serious offence in the UK could be tried for that offence by the Russian government.

Q&A How does diplomatic immunity work? Show Hide Diplomatic immunity is the protection given under international and UK law to foreign diplomats and their families. It was formalised through the 1961 Vienna convention on diplomatic relations (VCDR). Reciprocal global agreements also protect UK diplomats working abroad. Without a foreign state agreeing to lift immunity, diplomats and their dependent families can only be detained “as a last resort” if, for example, they are deemed to be a danger to others or themselves. The only other sanction available to the Foreign Office would be to order their expulsion. When a foreign state agrees to remove that legal protection, it is known as a “waiver of immunity”. Individual diplomats cannot do so; the embassy of the foreign state has to make a formal request. As well as covering diplomats and their families anywhere in the UK, the same convention and legislation prevents UK officials from entering diplomatic premises. That inviolability enabled Julian Assange to stay in the Ecuadorian embassy in London for seven years. Owen Bowcott, Legal affairs correspondent

Stephens said: “Anne Sacoolas was allowed to, or encouraged to be spirited away on an American transport plane and effectively rendered a fugitive from British justice.”

Jonathan Sacoolas, Anne’s husband, who was employed at RAF Croughton in Northamptonshire, is understood to work for the CIA, and the UK still says he and his dependants enjoyed immunity as staff at the base.

It is not clear how much choice Anne Sacoolas was given in the decision to fly herself and her family back to the US in a military plane, or how much either the Foreign Office or the Northamptonshire police resisted such a move in the hours immediately following the incident.

Stephens said: “They clearly decided they did not want any publicity, but had not expected the parents of Dunn to start campaigning as much as they have. Their handling of this has turned a tragedy into a disaster for them.”

In response to the letter, Dunn’s mother, Charlotte Charles, said the apology offered so far was not sufficient.

She told Sky News: “My opinion on Anne Sacoolas now wanting to come forward and say sorry – to be perfectly honest, yes, it’s the start of some closure for our family.

“Having said that, as it’s nearly seven weeks now since we lost our boy, sorry just doesn’t cut it.”

She added: “We’ve known from the start that the ‘extra’ feeling in the pit of our tummies, told us that something wasn’t right. We’re proud of ourselves for fighting for justice for Harry, and not ignoring this gnawing within our bodies.

“We’d rather have our beautiful boy back, but we are also elated that all this fighting for justice for Harry has not been in vain.”