Anne Sacoolas' legal representative, Amy Jeffress, said she would "continue to cooperate with the investigation".
Mrs Sacoolas left the UK under diplomatic immunity despite being a suspect in the crash with Mr Dunn, 19, in Northamptonshire on 27 August.
A statement said: "Anne is devastated by this tragic accident."
It continued: "No loss compares to the death of a child and Anne extends her deepest sympathy to Harry Dunn's family."
The statement, issued by law firm Arnold and Porter, said Mrs Sacoolas had "fully cooperated with the police".
It added: "She spoke with authorities at the scene ...
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