Judge Alister Abadee told the NSW District Court in Gosford it was "something of a miracle" the victim had survived the "vicious and ferocious attack".
"The attack was unprovoked, inexcusable and carried out against an innocent person," Judge Abadee said on Thursday, when jailing Begg for 13 years and six months with a minimum of nine years and four months.
Paramedics found the victim, 35, lying in a pool of blood in her public housing apartment at Ourimbah on the Central Coast on July 3, 2023, with an open wound to her head and her brain on show.
The judge said police later went to Begg's nearby apartment in the same complex and were refused entry but had sufficient time to notice bloodstained shoes in the bath, a hammer on a shelf and the victim's dog inside.
Begg, who had been on parole for assault, was not arrested and only agreed to be interviewed by police later that day before denying any involvement in the attack.
She then attacked another woman at Wyong on July 19, 2023, with a carving knife, cutting her right knee and stomach.
Begg finally admitted the attacks a month later, telling police she had been jealous of both women and their relationships with her former boyfriend.
In the hammer attack, Begg said the victim had slept with her boyfriend about a year earlier. When she had found out, she broke up with him.
The victim, 35, was so badly beaten she needed a titanium plate inserted to replace her shattered skull.
She spent three months in hospital after suffering multiple skull fractures and still requires 24-hour daily care, including a hoist to lift her in and out of bed. She will remain in a wheelchair for the rest of her life.
The judge said Begg told police there was some "jealousy s***" between her and the hammer victim before admitting, "I got to have a bit of fun and I'm spewin the bitch isn't f***en dead".
"And trust me if I get out she's going to be dead and so is (Begg's ex-boyfriend). I plan on having a hell of a lot more f***en fun and that's that."
Judge Abadee said Begg had an extensive criminal history and once told prison officers "I'm the most violent inmate here".
Begg's parents had been drug addicts and alcoholics, and her mother was a sex worker.
The judge said Begg, diagnosed with a borderline personality disorder, intermittent explosive disorder and substance use disorder, had threatened to violently reoffend against the two victims when released and her prospects of rehabilitation were poor.
He said both victims had done nothing to provoke Begg who appeared to have developed a "brooding resentment" towards them over some period of time.
Begg had pleaded guilty to causing grievous bodily harm by wounding with intent to murder, assault occasioning actual bodily harm, intimidation and destroying property.
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