Mundy had been riding in the annual Kurow Cup race Sunday when her mount, Elleaye, clipped heels and fell at the 600-meter mark of the race, the Brisbane Courier-Mail reported Monday.
Emergency crews flew her to a hospital in Dunedin where she was initially listed in critical condition. It is believed she was galloped upon by a horse during the fall, the report said.
The New Zealand horse racing community has been hit hard by Mundy's death, trainer Lisa Rae told the Courier-Mail.
"She's the wrong person -- she's been taken too soon," Rae said. "She'd rock up every morning ready to ride -- she was just one of those people who have a natural way with animals."
"Our owners are broken, they're distraught. Ashlee was just lovely, she's touched so many people's lives," Rae added.
The New Zealand Racing Integrity Unit was expected to conduct an investigation into the accident, interviewing other riders and viewing race video, the newspaper said.
The condition of the horse was not reported.