Hansen, 30, was arrested Wednesday in Manoa after she allegedly fled the scene of the accident.
Police said she followed Elizabeth Conklin to her condo and witnesses then saw Hansen hit Conklin with her car. Hansen then reversed to attempt to hit Conklin a second time.
A bystander saw the incident and said he broke Hansen's rear window, at which point the surfer left the scene.
"He saw her in her car getting ready to hit me again. He totally saved my life," Conklin said of the bystander.
Hansen was being held on $1 million bail.
Conklin had cuts and bruises on her body and was taken to a hospital for treatment.