After witnessing the showdown the two flew to the US for treatment on August 11.
A source close to Winehouse said that the singer was really upset after seeing her parents take on her in-laws in an argument about their addiction.
"It broke Amy's heart to see her parents and in-laws fighting. That was the point when she realised all the drink and drugs were causing huge problems for everybody," the Mirror quoted the source, as saying.
The couple met up with a leading Harley Street doctor recommended by former wild child Kelly Osbourne before they headed to the US.
They have assured their parents that everything will be fine."Please stop crying, everything will be OK," Fielder-Civil told his mum.
Amy told her mother-in-law: "I'm so sorry. I love you. Please don't worry," Winehouse assured her mum-in-law.
The 23-year-old and her hubby are sharing a room at the facility and have surrendered their cell phones to avoid contact with the outside world.
Last week, Winehouse passed out at her home following a three-day drug and alcohol binge,
She was rushed to the hospital at one in the night. Later in the week, her friend caught her taking heroine in a suite.
Hearing the news, Winehouse and her hubby's worried parents met up with Fielder-Cavil's family and during the row, the rehab star's dad caught the studio assistant's step father by his collar and 'threatened to rip his head off'.
"It was only when Amy saw her family falling apart that she realised she had to do something,' the source said
"She confessed that she and Blake had drug problems and had to have treatment together."
"They both admitted taking cocaine and heroin. But they denied they had been injecting heroin."
"At one point, both Amy and Blake stripped off in front of Georgette to prove they had not been using needles. But they now realise that if they don't get help now, they will both die young. This is their watershed, their wake-up call."