She said the race was "unnecessary stupidity" and robbed her teenage daughter of "dreams [for] a 21st, a wedding, and maybe one day children".
Maree's death "has changed a lot of lives"but ultimately "we have lost a family member forever".
She displayed apparent anger towards O'Sullivan, who sat in the dock, when she said: "We don't call it an accident because it was planned."
"[O'Sullivan] has had 18 months of extra life that Maree will never have and she will never be able to experience the dreams she had."
Crown Prosecutor Steve Manning said: "All who took part in the race were dicing with death."
"It was an act of utter stupidity that has ended with the most serious of consequences," he said.
He said "remorse was not available "for O'Sullivan as a possible discount for his prison term because the 21-year-old "simply refuses to accept [responsibility]".
O'Sullivan's lawyer, Scott Jefferson, said the tragedy was a result of "the failures and shortcomings that often come with youth" and the false perception that "indestructibility" teenagers hold.
"It is obvious to say their was an absolute failure to think ahead and see the consequences of [O'Sullivan's] actions".
He said it was clear to him that his client had been remorseful from the beginning, which he claimed was evident with O'Sullivan stating in a police interview, "if only I could turn back the clock, I would".
A "heartfelt"note from O'Sullivan was passed to Judge Jonathan Down before he cast down his sentence.
Judge Down said a jury simply refused to believe O'Sullivan when he attempted to extirpate his guilt in the tragedy by saying he braked and slowed down, well ahead of the next intersection, which was the designated finish line.
He said O'Sullivan "aggravated [his] offending" because he was disqualified from driving at the time of Maree's death and had also been convicted of sustained loss of traction while driving in the past.
Judge Down added the letter of remorse he was handed today was "too little, too late" and was in stark contrast to the pre-sentence report which stated O'Sullivan showed a "lack of insight into [his] involvement".
"Your attitude is one that is characterised as lacking insight and lacking remorse to the extent of almost blaming other people for what happened on that night," Judge Down said.
He sentenced O'Sullivan to three and a half years in prison and disqualified him from holding a drivers license for four years.
O'Sullivan will join Lawrence, his brother Adam O'Sullivan, and Jesse Ellmers in prison.
"This is a family that will now see two of their sons in prison as a result of the same event," Mr Jefferson said.
Late last year, Lawrence, Adam O'Sullivan, and Ellmers, were each sentenced to two years and three months' imprisonment for their involvement and disqualified from driving for four years.
The trio were the first in the country to be sentenced under then Police Minister Judith "Crusher"Collins' tough new legislation against boy racers with the Sentencing (Vehicle Confiscation) Amendment Act and the Land Transport (Enforcement Powers) Act.
The legislation was described as "Maree's law"
by her mother in court today.
Adam O'Sullivan and Ellmers appealed their sentence but they were dismissed in the High Court in April.
Matthew O'Sullivan has been sentenced to three and a half years in prison for his involvement in the death of Maree Schafer during a drag race near Napier in 2013.
Appearing in the Napier District Court today, O'Sullivan, 21, was sentenced to three and a half years in prison. He was last month found guilty of racing causing the death of Ms Schafer, 18, on February 19, 2013, and racing causing injury to a passenger in the crash on Sandy Rd, Meeanee.
O'Sullivan was the driver of a Ford Falcon racing a Holden Commodore carrying Ms Schafer and the other passenger, and driven by Brandon Lawrence.
Having raced at speeds exceeding 180km/h on Awatoto Rd, on Napier's southern boundary, O'Sullivan slowed at the intersection of Meeanee Rd, but Lawrence accelerated, lost control and hit a tree.
Lawrence later admitted causing the death and injury, but, O'Sullivan pleaded not guilty to the charges of being a party to the offences.
