In reference to how she uses her movement to play a character (physicalization), I was struck by how important that is on the weekend when I saw the film Amour starring Emmanuelle Riva and Jean Louis Tritignant. Their movements were essential to how they played their characters. It was incredible work by two great actors who are veteran performers. And here is Summer, about a third of their ages, talking about her use of her physical movements to show us key elements of her character through how Cameron walked, how she reacted to people, how she looked at things, and so on.
This use of the body and the control of the body to tell a story must be incredibly hard work. Clearly, Summer Glau is able to pull this off to good effect.