Sylvia Brown caused life-changing brain injuries to 23-year-old Amy Lawrence when she crashed into her in Cranbrook, Kent after smoking cannabis and taking prescription drugs.
Despite slurring her speech and falling asleep as she spoke to police and paramedics in the aftermath of the crash on November 2, 2015, Brown initially claimed she had taken nothing stronger than cough syrup on the morning of the accident.
Blood tests later revealed the cocktail of drugs she had taken including prescription oramorph and codeine.
The 53-year-old lied to police telling them the traces of cannabis came from passive smoking at a party the week before the horror smash.
During her trial Brown admitted she had 'made a mistake in panic' and that she was in fact a regular user of cannabis, smoking a joint each night before going to bed.
She maintained however that she had not consumed the drug on the morning of the accident, or taken her prescription morphine or any codeine.
But today Brown's trial took a dramatic turn when she changed her plea and admitted causing serious injury by dangerous driving. Brown, who suffers from chronic obstructive pulmonary disease, said the only medicine she had taken the day of the crash was Benylin cough syrup.
She was driving her Honda Civic when she ploughed into Miss Lawrence's Mini Cooper convertible at about 5pm.
The Honda, said to be travelling at 40mph, struck the side of Miss Lawrence's car, forcing it onto the pavement and a grass verge.
It left the keen equestrian with a brain injury which causes her both short and long-term memory loss, mood swings and constant headaches.
The court heard she also sustained a hairline fracture to her breastbone, a sprained coccyx, an ear injury which has caused permanent tinnitus, and fractures to her left hand that required three operations but resulted in nerve damage and loss of grip.
She can no longer ride or drive, and has been unable to return to her job as an accounts administrator.
The court heard Brown was prescribed the morphine-based painkiller two months before the crash.
She said she usually took a dose every two to three days. She had also recently moved house and told her GP in October that she was anxious and under 'great physical stress'.
But her doctor warned her of the implications of oramorph on her driving ability, the court was told.
The force of the smash on the A229 Hartley Road between Cranbrook and Hawkhurst flipped Brown's car onto its roof. It then skidded along the road before striking a Ford Mondeo, driven by a work colleague of Miss Lawrence's.
Brown made no attempt to slow down or swerve as she veered across the chevrons separating the lanes of the straight and wide road and into Miss Lawrence's path.