Three years on from the horrific attack the scars - both inside and out - remain, as the 25-year-old fights to move forward with a life that will be forever changed.

It has been a difficult road for the once bubbly mother of four, who has lost custody of her children and struggled with anxiety in the wake of the attack.

In another blow, Ms Sullivan was left devastated by the news that her attacker, Adam Scott Murray, won an appeal to have his 20-year prison term set aside last week after successfully arguing the sentencing judge should have removed himself from the case.

He will be re-sentenced in the District Court, leaving a question mark hanging over how much time he will now serve.

The news came as a shock for Ms Sullivan, who still lives in fear despite knowing her attacker is behind bars.

"[Since Murray was sentenced in August 2013] life has still been very unsettled, I still worry and think it's not over," Ms Sullivan said.

"I still look over my shoulder all the time, every day, no matter where I am or who I'm with. I don't feel safe any more."

On the night of the attack, an intoxicated Murray, who had only recently been released from prison on parole, armed himself with a gun and went to the home Ms Sullivan shared with her 27-year-old partner and their four children.

He knocked loudly on the front door and when Ms Sullivan opened the curtain in the window at the side of the door to see who was there, he fired the gun, hitting her between the eyes.

Murray later told a psychologist he felt under threat from Ms Sullivan's partner and had gone to the house to "scare him off".

Miraculously, Ms Sullivan survived the horrific attack but required several surgeries to realign her left eye and remove the bullet from her brain.

She remains on the waiting list for another series of surgeries to reconstruct and open the left eye.

Murray, who had previously been jailed for barging into a Warrawong home and stabbing a man, pleaded guilty to one count of discharging a firearm with intent to cause grievous bodily harm in February 2013.

District Court Judge Paul Conlon sentenced him to 20 years' jail, with a non-parole period of 15 years, in August 2013.

In April 2015, lawyers for the 28-year-old successfully argued to have that sentence put aside on the grounds Judge Conlon refused to recuse himself during sentencing proceedings due to perceived bias.

Ms Sullivan will return to court for the re-sentencing, in the hope her attacker is locked away for as long as possible.

"I'll be there. I want to be sure he gets more time or at least what he was given last time," she said.

"If he got less I'd be devastated. He is a violent person, he shouldn't be around people at all."

Ms Sullivan's mother, Karen Carlson, is one of many of the loving family members who have rallied around her in support.

She said the family had been left angry and confused by the decision to re-sentence Murray.

"I'm worried that he will get off on a lighter sentence. One hundred years isn't enough for him, in my eyes," she said.

"To go through all of this again is devastating.

"We will be forever haunted by what he did on February 15, 2012."