The 12-year-old suffers from a one-in-a-million kidney disease called Dense Deposit Disease (DDD), which stops the kidneys from filtering waste from the blood.
But health bosses are refusing to pay for the Eculizumab drug, which costs £393,000 a year, because her condition is too rare to be covered by the national funding policy, but not rare enough to qualify as an exceptional case.
And the drugs are kept under lock and key at Leeds General Infirmary where she is treated.
Abi, of Robin Hood, has now been given new hope after a case review by the National Institute for Health and Care Excellence (NICE).
The watchdog published new evidence showing 70 per cent of patients had a positive reaction to the drug.
The report said: “Eculizumab improved or stabilised signs of C3 glomerulopathy DDD in seven cases.
“A partial response was seen in one case, and it was ineffective in two cases.”
And the evidence is now being considered by NHS England, who could reverse their decision and give Abi the drug.
A decision is expected to be made within the next few weeks.
Her dad Andy Longfellow said: “This is a big milestone towards getting the drug, not only for Abi but for other sufferers aswell.
The drug has never been looked at by NICE before so the findings are encouraging.
“Abi was over the moon when she heard the news but we know this is only the first step.
“It could change her life.”
Abi, who spends 10 hours a day on dialysis, was diagnosed with the disease aged 10 when a trip to A&E for a throat infection revealed she was suffering from the kidney disease.