The woman was working as a Woofer (Willing Workers on Organic Farms) at the time of the incident in exchange for food and accommodation.
In June 2018 she was travelling as a passenger in the side-by-side when the driver lost control and the vehicle fell 13m down a hillside.
The woman was ejected from her seat, and the vehicle eventually came to rest on top of her and she died from crushing injuries.
The driver was also thrown from the vehicle, and suffered minor injuries.
The WorkSafe investigation found one door of the side-by-side had been removed and that both seatbelts and helmets were not being used, contrary to manufacturer and WorkSafe advice.
The investigation also found that one seatbelt was not working, and the driver's seatbelt warning system was not working.
"The safety of the vehicle had been compromised," WorkSafe's Area Manager Danielle Henry said.
"Safety features fitted to the vehicle had not been maintained. However, the business still allowed workers and visitors to the farm to operate an unsafe vehicle.
"These vehicles are used every day on farms right across the country. They have safety features for a reason and maintenance of these is imperative. If those features aren't working as they should and you can't supply appropriate personal protective equipment, then no one should be driving it."