Lissie Harper said the 16-year sentence handed to Henry Long and 13-year terms for Albert Bowers and Jessie Cole were too lenient for their “heinous” crime.
Ms Braverman yesterday condemned the “horrific crime” and referred the case to the Court of Appeal.
Newly married PC Harper, 28, was killed when he was dragged behind a car after responding to a 999 call in Berkshire last August.
Getaway driver Long, 19, admitted manslaughter and Bowers and Cole, both 18, were convicted of the same offence.
Praising Ms Braverman’s swift response, Lissie, 29, said: “The sentences for Andrew’s killers did not match their heinous crime. It was not justice and it needs to be addressed.”
Lissie is campaigning for a Harper’s Law under which those who kill emergency service workers must spend the rest of their lives in prison.
PC Harper’s mother Debbie Adlam said: “The whole nation stands with us in outrage at the sentences handed down to my son’s killers.