Athena Vibert sobbed on Friday as Judge Antony Townsden read out the details of the accident that claimed the lives of Wilton's Julie Bullock, 49, and her seven-year-old son Hudson.

The NSW District Court judge jailed Vibert for three-and-a-half years with a non-parole period of 18 months.

The fatal crash on the Hume Highway near Wilton in 2017 also left Hudson's twin sister Sienna fighting for life.

Vibert, 52, previously pleaded guilty to two counts of dangerous driving occasioning death and one count of dangerous driving occasioning grievous bodily harm.

She had, on four occasions, lied about her epilepsy while applying to renew her license, ticking "no" next to a question asking if she suffered from the condition, the court heard.

She had not taken her anti-convulsant medication on the day of the accident because she was due to have a blood test.

Darren Bullock, Julie's husband and Hudson and Sienna's father, said he was disappointed with the sentence.

"Eighteen months for killing two people and hurting Sienna the way she was hurt seems a bit light on. It was an avoidable accident," he said outside court.

The court heard fragments of a letter Vibert had written to the Bullock family.

"I wish I had died instead of them," she wrote. "Not a second of my life goes by when I don't think of you and your family ... I died that day."

Mr Bullock said that while he'd let go of his anger, he didn't accept Vibert's apology.

"It didn't really show much remorse at all ... it was scripted," he said.

"She's still breathing. Julie and Hudson aren't. Physically (Sienna) is OK but she misses her mum and her brother greatly.

"To me, it's a bit like she was literally drink driving."

As a weeping Vibert was led away after being sentenced, she turned to her family in court, blew them a kiss and said: "I love you. Look after each other."