"The cow also landed on her - but she was not trapped,'' a statement said.
A member of the chopper crew told the Herald they touched down on a road near where the accident happened, after ambulance staff initially treated the young woman at the site before moving her to the road.
Family members had also arrived at the scene by the time the helicopter got there.
The victim was conscious and was able to talk to the crew.
"She's most likely gonna be okay,'' the staffer said.
The teen was airlifted to Auckland City Hospital in a serious condition.
Asked about the cow involved, the crew member said: "I'm not too sure how the cow is.''