Kota Belud Police Chief Supt Mohan Nadasen said preliminary investigations showed that the four-wheel-drive came from the Ranau direction, while the teacher was from the opposite direction in the 6.30am incident.
He said it was believed that the four-wheel-drive tried to overtake but failed, resulting in the collision with the teacher's vehicle.
"She was rushed to the Ranau Hospital and subsequently taken to the Queen Elizabeth Hospital due to serious bodily injuries," he said, adding that the woman is said to be in stable condition.
No one else was injured in the accident.
He urged witnesses to contact the Kota Belud Police Traffic and Compliance Chief Insp. Narzuan Mohd Noor at 088- 976 600 or 019-261 6595 to facilitate investigations.