How Did Sabrina and Wiesom Burn Sophie's Body?

Gareth Walton's statements placed both Sabrina and Wiesom at the scene of the crime, completely shattering the narrative that one of them acted alone in assaulting Sophie while the other person slept. The couple had essentially held Sophie prisoner inside their home for six weeks during which time they withheld food until she agreed with whatever they demanded just to eat. They also forced her to sleep in a tiny dark room where she withered away. It wasn't clear if she had been killed by accident during one of the torture sessions or if the couple decided she had to die. Both pleaded guilty to perverting the course of justice by burning Sophie's body, but not guilty to her murder.