Given my general reluctance to read straight theory, my thesis advisor kindly found a handout called "Butler for Beginners" that neatly sums what Judith Butler has to say about gender performativity without all of the lofty academic-speak. I'm not going to get deeply into Butler's theory, but let it suffice to say that Butler basically says that a) gender and sex are constructed and b) it is through repetition and performance that we take on a gender role. Obviously, Hornbacher, by attempting to conform to cultural standards of femaleness by starving and binging/purging, constructed herself as female by her behaviors, but I'm reluctant to say that that fact is significant in the context of my thesis. I don't think Hornbacher's eating disorder or life story has so much to do with engendering herself as it has to do with being engendered. Because she was treated "female", she acted female, and an eating disorder ultimately resulted (I'm simplifying things too much here). I'm not sure that by repeatedly performing as female she constructed herself as a woman and, as a woman, then performed a traditionally female illness by having an eating disorder.
Maybe I'm being too resistant to the thought that gender performativity could cause eating disorders (or maybe I'm misinterpreting things), but I just don't think the hows and whys about how gender develops in the first place have much to do with the work I'm trying to do (what work is that?).