More than 88,000 people have signed an online petition calling for a new inquest to be brought forward for Kevin Williams, a 15-year-old victim of the 1989 Hillsborough disaster, whose mother, Anne, has been diagnosed with terminal cancer.

The attorney general, Dominic Grieve, is preparing a high court application to quash the original Hillsborough inquest verdict, after the report of the Hillsborough Independent Panel in September discredited its principal findings.

The petition seeks to enable Anne Williams, who has campaigned relentlessly against the inquest since its jury reached a verdict of accidental death 21 years ago, to see it quashed in her lifetime.

Elkan Abrahamson, Williams's solicitor, said he believed it should be possible for Grieve to complete his application by the end of November and for the high court to hold the hearing before Christmas.

However, Grieve's office, which has said he will make the application "as soon as he possibly can", hopes only to have a draft completed by the end of this month. When the online petition reaches 100,000 signatures, the issue will have to be considered for a debate in parliament.

"It is fate," said Williams, who has now moved to a hospice in Southport, Merseyside. "I have known all along what the inquest said about Kevin was wrong, that witnesses were pressured to change their evidence. I couldn't let go, for my son. I do want to see the inquest quashed."

Williams said she has not asked her doctors how long she has to live: "I am taking each day as it comes."

She always contested the account given at the inquest that Kevin died from traumatic asphyxia and so could be considered irrecoverable by 3.15pm on the day of the disaster. That was the time limit for inquest evidence set by coroner Dr Stefan Popper, thereby excluding the emergency response from being considered. Williams was part of an application for a judicial review by six families in 1993 which saw the inquest upheld; she made three applications to the attorney general for the inquest to be quashed, which were refused; and her 2006 application to the European court of human rights failed because she was out of time.

In September, the report by the panel, chaired by James Jones, the bishop of Liverpool, vindicated the campaign by Williams and the other Hillsborough families who protested that the inquest did not reach the truth or justice about the disaster. The panel found 41 of the 96 people who died might have been saved after 3.15pm had the medical response been competent.

"I already knew that Kevin did not die of traumatic asphyxia and he could have been saved," Williams said, "although I am very pleased with the panel's findings."

Over years of campaigning, Williams made contact with two people who had helped Kevin: Derek Bruder, an off-duty police officer, who had felt a pulse in Kevin after 3.15pm, and special police constable Debra Martin, who said Kevin had opened his eyes and said "Mum". Both changed their statements following visits from West Midlands police officers, to suggest there had been no signs of life, but later emphatically stood by their original statements and said they had been pressured to change their evidence to comply with the view that Kevin could not have been saved after 3.15pm.

Dr Iain West, a consultant forensic pathologist at Guy's hospital in London at the time of the disaster, decided on a review of Kevin's details that he died from severe neck injuries and might have been saved.

Grieve's office said: "The attorney general is deeply saddened to hear of Anne Williams's diagnosis. He continues to give this matter priority."