She might have possible genetic anomalies that could alter structure and give her a difficult time running. Have a PT or doctor take a look at her pelvic tilt. Depending on which way her pelvis may be rotated can have an effect on her gait. Beyond that it just sounds like she has poor running technique. One of the best ways to teach technique is skipping drills and hurdle runs. These drills will help teach knee lift while also teaching the proper way to drive force down and back into the ground effeciently. It is difficult to describe each drill so you can visualize how it should look. My mentor produces a DVD which is probably the best movement skill resource available. You can find it at:
www.sportsspeedetc.com If you have any further questions I'm available at
hoopdreams51@aol.com. If you do get the DVD I'm the big guy demonstrating many of the drills. You'll be able to see how adjusting technique has allowed for a bigger guy like myself to move like I was much more compact.