This is going to be similar to an answer previously posted. I would say that one critical step in outlining this theme is to go through the story and make the argument that there are two Walkers being presented throughout much of it. The life of being "the prettiest" or the one deemed with beauty has to be contrasted with how life was after the accident. What do you notice internally about the protagonist in both realms? Along those lines, I think you have to delve into how life was for Walker after the accident. The struggle that emerged might not be directly linked to the cosmetic disfiguration, though some of it is. Yet, I think that you want to make the argument that Walker, to a great extent, experiences imprisonment when she is considered to be "ugly." This imprisonment happens on a social level, even going to a school that used to be a prison and being called a "one eyed bitch." Yet, there is much more of this imprisonment on a personal level, where Walker rages about her predicament and not merely why what happened happened, but why did she change as a result. I would pay attention to those moments where she reflects about whether she changed or the conversation with the brother who accidentally shot her. These might be good points to bring out the imprisonment that she experiences. At the same time, I would say that the ending might also be important in that it represents a moment where she is able to no longer rage against the person she is, but rather dance "in peace" with whom she is, the experience of being both someone who is beautiful in a sense that transcends social or human conventions. I would focus here in developing an essay on imprisonment in the short story.