The woman, from Derby, was westbound in a green Alfa Romeo just before 7pm when she was in collision with a tractor, also westbound.
The tractor was towing an enclosed trailer with 30 lambs on board.
The Alfa left the road and the woman had to be cut from the wreckage. She was taken to Derriford Hospital where her injuries were described as serious, but not life-threatening.
The tractor driver, from Hatherleigh was not seriously injured, but 14 of his lambs were killed. The road was closed for three hours.