Most read: Young girl hung from tree with skipping rope in school yard bullying incident - 'She was saying no, no, no'

A young girl with a heart condition has been left severely traumatised and "broken" after a bully at her Perth school hung her from a tree with a skipping rope, her mother says.

"It's unbelievable that another child committed such an act of violence against her and that's how we could have lost her," a tearful Belinda Yoon told Nine News of her 10-year-old daughter Amber, who she described as already having endured "more surgeries than we can count and been in the scariest situations".

The incident became national news in Australia last week after Ms Yoon spoke up about it on Facebook.

"She put (the rope) over her neck and started wrapping and wrapping and wrapping," Ms Yoon told Nine News of the school playground incident. "She was saying, 'No, no, no,' until she couldn't speak anymore."

She said her daughter, a Year 5 student half the size of children her age due to her heart condition, thought she was going to die as her toes barely scraped the ground.

The incident is now under investigation by police, and Ms Yoon says she has removed her daughter from Queen of Apostles Catholic school, where the playground incident is alleged to have taken place. She accused the school of not contacting her about the bullying or seeking medical attention after the incident.

She only found out about it, she said, after reading her daughter's journal.

"She's such a tough little cookie," the mum told Nine News. "I really that hope this has not broken her spirit, because that for me is what would be unforgivable."