Kyesha Finemore suffered an "abominable" attack that left her with burns so bad she spent days in an induced coma and nearly a month in hospital.
Brae Taylor Lewis - her boyfriend of about two years at the time - admits he was responsible.
The pair were both 17 years old and under the influence of meth at the time of the attack in May 2016.
They got into an argument when Ms Finemore asked to use a mobile phone they shared.
Lewis threw a beer bottle containing fuel at his girlfriend, the flammable liquid splashing on her.
As she put her hands up Lewis extended his left hand while flicking a lighter.
"The fumes which were emitting from the fuel in front of the flame ignited and caused the front of her body to become engulfed in flame," Brisbane District Court Judge Michael Burnett said.
One witness told police Ms Finemore's skin was peeling from her arms and upper body.
The teenager was taken to hospital where she spent days in an induced coma.
Doctors found 21 per cent of her body was burnt.
She needed several surgical procedures and was left permanently disfigured with scarring to her arms, chest, abdomen, back and thighs.
The impact of the incident has been devastating and life-changing for her, Judge Burnett said in sentencing Lewis on Thursday.
Ms Finemore told the court her sleep is disturbed by recurring nightmares, she is "petrified" of putting fuel in her car and the damage to her skin makes her sensitive to soaps, sanitisers and the sun.
She is also self-conscious of her scars and appearance.
"I found myself crying all the time ... and there were times I thought of giving up," she said.
"I have been forced to learn how to cope with the permanent injuries and scarring that this brutal assault has left me with.
"This is a life sentencing for me that I must endure and cope with every day.
"No matter how much time passes this will always stay with me."
Ms Finemore's mother told the court her daughter spontaneously bursts into tears when she looks in the mirror.
Lewis, now 22, had earlier successfully appealed a conviction by a jury and an 11 year jail term.
He was due to face a retrial this week, but after a delay because of Brisbane's COVID-19 lockdown, Lewis instead pleaded guilty to one count of malicious act with intent.
Judge Burnett said Lewis' offending was "horrendous and disgraceful", but a sentence needed to take into account his youthfulness, remorse, rehabilitation efforts while in custody and guilty plea although it was at a late stage.
"The object of a sentence in a large part - apart from punishing you for this abominable behaviour - is to assist you in your rehabilitation," Judge Burnett told Lewis.
"Take advantage of those opportunities and you will find your parole release will be sooner rather than later."
Lewis was sentenced to nine-and-a-half years in jail.
With time already spent in custody since May 2016, he will be eligible for parole in six months - after serving half the term.
Defence barrister Andrew Hoare said Lewis was exposed to violence and trauma in his childhood, and developed a drug habit from the age of 15.
