EDMONTON -- Social worker Sheli Steil remembers when two-year-old twin girls were taken to hospital after being beaten, neglected and starved.

One of them weighed 13 pounds -- the size of a six-month-old baby. She was "just skin and bones" and not expected to live.

Her sister, who was in somewhat better shape at 16 pounds, had little hair and couldn't walk. The child was fascinated when a doctor gently touched her hand, said Steil.

"She was mesmerized, as if no one had ever done that before."

Steil, whose office took custody of the girls shortly after they arrived in hospital, read a victim impact statement in an Edmonton courtroom Monday at the start of a week-long sentencing hearing for the girls' mother.

The 37-year-old woman, who can't be named, has pleaded guilty to manslaughter in the death of one twin, known as M, and to aggravated assault and failing to provide the necessities of life in relation to both girls.

She has admitted that she didn't provide her daughters with adequate food and that she assaulted them over a prolonged period of time. Court hasn't heard any explanation as to why.

Crown prosecutor Shelley Bykewich is asking a judge to sentence the mother to between 23 and 25 years in prison. The defence is to give its recommendation later in the week.

The twins' father was sentenced last year to 15 years on the same charges. Court heard he didn't physically injure the girls but did nothing to stop their suffering.

The parents immigrated from Algeria in 2008 and their three children were born in Edmonton.

Bykewich said a psychiatric assessment found no evidence that the woman, who described herself as a "good mother," had a mental illness. She's an educated woman who was learning English and didn't appear to be culturally isolated in Canada, the prosecutor said.

"This was not a situation of a single, overwhelmed parent whose frustration has hit the breaking point."

On May 25, 2012, paramedics were called to the family's home and found the twins sitting in infant car seats. Skin was hanging from their bodies, their ribs stuck out of their chests and they were covered in scabs and bruises.

Their four-year-old brother was healthy. The kitchen was stocked with food.

The smallest girl wasn't breathing and spent several months on life support in hospital. The parents, citing their Islamic beliefs and love for the girl, fought in court to keep her on machines despite the advice of doctors. Two Alberta courts eventually ruled the girl should be allowed to die and the Supreme Court declined to intervene.

An autopsy showed M died of head trauma and starvation.

Steil told court it was the worst case of neglect and mistreatment she and her co-workers had seen.

When the surviving twin was learning to walk, staff gave her a new pair of shoes that she never wanted to take off, Steil said. And when the girl's hair started growing in, she was given colourful bows that she wanted to keep on her head.

Steil said workers spoke regularly with the mother after her arrest to give her updates on the girl and her brother in foster care. The woman never asked about her daughter, only her son, she said.

Steil's office made arrangements for M's funeral and chose the words for her headstone.