GOT strength?

This morning my daughter & I went to run inside as it is 0 degrees outside. We ran on a local indoor track which as you can image was fairly crowded. As we ran, I again found myself watching people warm-up and then accessing the way they run. There was a female teenage runner who was stretching her hamstring over her head. She obviously was very flexible. A few laps later, I saw her running. What I observed was the following: as she landed and went to foot flat, her swing leg's hip dropped several inches, creating an un-level pelvis. On the stance leg, her femur and knee rotated inward. As her leg went through swing, the knees almost touched. In other words she has a lot of wasted motion and it all started with the hip drop. These issues could eventually lead to injury. I have seen this gait pattern many times, especially in flexible young female runners. This type of runner is, dare I say TOO flexible! She could improve her running mechanics and prevent injury by actually spending more time strengthening. She needs to work on hip stability/ NOT flexibility. The exercises we have and will post are good examples of the type of functional strength training she would benefit from the most. These types of exercises work the hip and leg muscles in similar ways they are used with running. They are also functional mobility exercises which means that they require strength and mobility. Mobility she's GOT/ just no strength!