She was critically injured and flung 13m from the red Ford Falcon's wreckage before it burst into flames.
Waking up at the scene, screaming in pain, she remembers Williams telling her to "shut the f*** up" and looking disappointed that she was still alive.
Her unborn child was also lost in the crash.
And today at the High Court in Christchurch, the woman spoke about her long road of rehabilitation, ongoing mental trauma, depression, and fear that one day Williams will come after her again.
"I don't know how someone I came to love could do this to me," she said in her victim impact statement read to the court.
Williams, who is originally from Greymouth and has 48 previous convictions and a history of violence against women, earlier pleaded guilty to attempted murder, kidnapping, two counts of male assaults female, and impaired driving causing injury.
His actions in April 2020 were described this afternoon by Crown prosecutor Mitchell McClenaghan as being "extremely violent, extremely cruel, and extremely brutal".
The court heard today that Williams, who had a difficult upbringing and a long history of substance abuse, had kidnapped a former partner in his car in 2017 and threatened to drive them off a bridge at 120km/h. Williams also has convictions of violence against former partners in 2013 and 2016.
Given his escalating history of violence and threats towards intimate partners, McClenaghan submitted that a sentence of preventive detention – which results in an indeterminate prison sentence - was appropriate for Williams.
On April 4, 2020, two days after Williams had strangled his partner and threatened to kill her, she told him their six-month relationship was over.
A furious Williams bear hugged her before taking her cellphone and getting into his car.
She got in behind him, trying to get her phone back.
But when she tried to leave, Williams grabbed her and said: "You aren't going anywhere."
He drove off while holding her by her head.
She struggled to free herself and even tried to open the moving car's door to escape but Williams kept hold of her and pushed her head towards the floor.
Driving dangerously at speeds over 100km/h, Williams overtook traffic and going on the wrong side of the road.
At one point, he grabbed the victim's head and pushed her face into the windscreen to force her to look at the oncoming traffic.
He said he was going to kill her.
Travelling down Greers Rd in the Bishopdale area of the city, doing between 134km/h and 137km/h, Williams suddenly wrenched the steering wheel, causing the car to smash into a power pole.
The impact speed was approximately 112km/h to 117km/h.
Williams' partner was tossed 13m from the car which burst into flames.
Williams managed to escape unscathed but his victim was rushed to hospital and underwent multiple surgeries for a broken neck, spine fractures, broken leg, broken ribs, a fractured and dislocated shoulder, internal injuries, and massive bruising.
She spent months in hospital recovering and learning to walk again.
A 3-year-old walking with his family on the footpath narrowly escaped being hit by the vehicle but suffered superficial cuts to his arms and legs from shrapnel.
After his arrest, Williams was overheard by police officers muttering: "I was just trying to get rid of her".
Methamphetamine and cannabis were detected in his system.
In considering his sentence, Justice Cameron Mander found that Williams was at high risk of further offending against future partners if he was released from prison without effective treatment.
Justice Mander concluded that a finite sentence of nine years' imprisonment, which is to be served without parole, was preferable to preventive detention.