Weird story...not a lot of details right now, and names are not being released. 

On June 1,st at 10:19 pm, the West Yellowstone Police Department received a 911 call from a caller who reported that his wife had jumped out of their moving vehicle on Highway 20 approximately a quarter of a mile west of West Yellowstone.

The Gallatin County Sheriffs Office, the Hebgen Basin Fire Department, the West Yellowstone Police Department, the Montana Highway Patrol, and the Yellowstone National Park Service responded.

An ambulance with the Hebgen Basin Fire Department transported the 34-year-old female to a  spot in Idaho where they met a life flight helicopter from Air Idaho.  Air Idaho transported the patient to the Eastern Idaho Regional Medical Center in Idaho Falls, Idaho.

The patient was declared dead on June 5, 2012.  The incident is still under investigation.

Source:  Gallatin Media Center