Fiona Kenny, who phoned 111, said the woman's scarf had got caught in the back wheel.
In a panic, the 32-year-old mother rushed outside in the "torrential rain" and accidentally broke her front gate.
At first, Kenny thought the woman had a stroke because she was leaned sideways still sitting on the seat. But Kenny said when emergency services arrived "They took off her big raincoat which covered her whole body and discovered the scarf was wrapped around her neck," she said.
"Everyone was trying to keep her warm and dry," she said.
Kenny said she and her cousin had blessed the site after ambulance staff laid the woman down on her front lawn.
"It was a terrible sight ... I couldn't not do anything," she said. "It was so sudden and she passed away right here."
