If you have a sturdy fence around your track, set up a hurdle one lower than your standard heighth about 2-3 feet from the fence, depending on how tall your athlete is. have her stand on her lead leg side. If she is right lead leg, she'll stand to the right of the hurdle, etc. Have her lean forward arms on the fence and run her trail leg over the hurdle mimicking trail leg motion. It should be pretty fast paced, make sure her knee is staying above her foot and she's not swinging it out.
This is a drill I do everday along with other hurdle drills.