Rebecca is wearing her beige boots with hard soles she actually said to her friend Imogen before making the clip "Let's see if i can break his head beneath my boots" so here is the clip you can see this girl squatting down applying all of her weight on his head, she is pressing down as hard as she can she has great fun hurting her victim as Imogen films the action, you only have to see her victims face to see the pain he is in. (Clip is 3:06)