Mum Ebony Berry is said to have joined a 'pro-hunger' group and punished mentally disabled Markea Blakely-Berry by depriving her of food.
The 16 year-old was found dead at her home in Georgia, U.S. weighing less than 3 stone.
The disturbing story has been revealed by the American TV station, WOOD.
It said Berry, 38, faces charges of murder and first-degree child cruelty.
After Berry's arrest, Markea's family noticed that she had links via Facebook to a group which encourages hunger.
Markea's father Mark Blakely said he was shocked at the apparent abuse.
"I can't even understand it," he said. "How could anybody do that to somebody? You wouldn't even do your worst enemy that way."
Markea was born prematurely, which led to her having a mental disability which, according to relatives, led to her mother treating her child with hostility.