B.C.'s representative for children and youth says she's launching an investigation into how a 14-year-old girl with Down syndrome was left for more than a week beside her dead mother.

Mary-Ellen Turpel-Lafond wants to know how, despite multiple warnings by neighbours, family, ministry staff, and signs of trouble at school, no one acted before Amy Prentice was found emaciated and filthy beside her dead mother in the family's mobile home in September.

"I'm going to do an investigation," said Turpel-Lafond. "I'm going to ask the minister and deputy to sit with me, give a full briefing as they should have done in September after this incident, and then I will begin the process of taking evidence under oath to find out what happened."

Turpel-Lafond said she was "shocked" to find out about the condition of Prentice, who thought her mother was asleep and tried to nurse her back to health during as many as nine days with her in her home in Chilliwack.

"There's an open box of macaroni and cheese sprinkled on it, so you know she was trying to make my mom better while she's lying there dead on the floor," said Prentice's half-brother Mike.

He said his mother was addicted to prescription medication and struggled with alcoholism. He said she had isolated herself and Amy from the rest of the family, refusing to allow him to visit.

"Everybody knew what was going on," said another brother, Kevin. "You just had to look at the lady; she's got scars all over herself from falling down when she's drunk."

Staff at the ministry of children and families responded to a complaint from the brothers, but cleared the mother in their investigation.

"They did their own investigation saying the place was fine, my mom was fine, but she wasn't. She died a month and a half later," said Kevin.

Neighbours found her badly decomposed body more than a week later. Her family believes she overdosed.

Amy wasn't at school for more than a week, and the chair of the Chilliwack School Board told CTV News they are checking into whether the girl was a student and whether anyone should have noticed.

Kevin Prentice says a ministry staff worker flagged the case from the inside as well.

"The respite care worker told her boss and said there's something really wrong with Yvonne. Someone needs to do something," he said.

Turpel-Lafond says she was disappointed bureaucrats didn't bring the case to her attention months ago. She said her office will follow Prentice's case to make sure she receives adequate care from here on in.

"I'm going to make inquiries and make sure this young girl is well supported and isn't bouncing from foster home to foster home," she said.

With a report from CTV British Columbia's Jon Woodward