They staged an elaborate fake robbery/arson, in which Lisa acted the part of the victim bound with duct tape and trapped in the walk-in cooler, while her co-conspirator started a small fire and walked off with a duffel bag of cash. A key part of their plan was a quick "rescue" of Lisa by the local fire department.
Unfortunately the wastebasket fire went unnoticed until the morning shift arrived to find a slow-burning smolder that had never erupted into the desired blaze. The air from the open door caused the smolder to burst into flames, and firefighters were summoned. They found Lisa in the freezer, chilled and semi-conscious, and rushed her to a hospital where she died from hypothermia.
When police nabbed her bungling 34-year-old accomplice with the cash stashed in a Burger King bag, she tearfully confessed the details of the crime, implicating Lisa in her own death. Her account was verified by the fact that Lisa's body showed no signs of forced restraint, the duct tape was loose, and she could have easily freed herself from her bindings and escaped from the unlocked refrigerator.