Georgia Gabriel-Hooper was just 14 years old when she witnessed her step-father murder her mother Cheryl in Newport in 2018.
Cheryl had finally escaped her abusive marriage just 48 days before her murder at the hands of Andrew Hooper.
Hooper was sentenced to life imprisonment with a minimum of 31 years for her murder.
Now, at 19 years old, Georgia has helped create a documentary about the horrific killing, hoping it will raise awareness of domestic abuse.
Speaking on ITV's This Morning ahead of the release of the ITVX documentary on Thursday, Georgia revealed the intricate nature of her stepfather's abuse.
She said: "It's incredibly complex, and it's something that takes a long time to understand. [At the time] It felt like there was something not quite right.
"He was incredibly coercively controlling, if we went out we'd get the silent treatment. He isolated her, it was a lot easier for her to not go out to not have to deal with his reaction.
"He was threatening and intimidating. He was a big guy and my mum was only small. The violence wasn't needed, he was incredibly intelligent and was able to tie my mum up in knots."
She said the first time Hooper was physically abusive towards Cheryl was the day he took her life.
Georgia hopes that speaking out about the layers of abuse will spread the word about the silent world of coercive control.
She said: "It's something that's not talked about, especially in the countryside there's still some very backward views on domestic abuse.
"Not a lot of people know what coercive control is.
"It's like carbon monoxide poisoning. You can't see it, you can't smell it and you can't taste it until it's too late.
"Every situation is different and each comes with their own risks, but there is a life after abuse. It doesn't always end the way it did for my mum."
The documentary, A Murder in The Family, will be available on ITVX later on Thursday.
* Women's Aid offers a free support line for anyone who is affected by domestic abuse on 01708 765200.