I think that Anderson features several topics in Wintergirls that could be the focus of some compelling essays. One topic is the role that body image plays in modern girls. The focus of Anderson's work is how body image can be a haunting reality for all teens. Cassie and Lia are both afflicted with such a condition. The idea of how consciousness is impacted by eating disorders helps to give the book its title: "You're not dead, but you're not alive either. You're a wintergirl caught in between two worlds. You're a ghost with a beating heart." The perceived springtime of youth is offset with the wintry affliction of life with an eating disorder. An essay on how eating disorders impact youth as seen in Cassie's and Lia's narratives would be compelling. It would reflect one of the most dominant issues in the novel.
Anderson's work speaks to how individuals can reclaim themselves from a condition of "winter" that might seem irredeemable. This is seen in how restoration is viewed as a process which takes time: “There is no magic cure, no making it all go away forever. There are only small steps upward; an easier day, an unexpected laugh, a mirror that doesn't matter anymore.” In seeing Lia's progression and Cassie's destruction, an essay could be constructed on how human beings are show to possess both realities with them. How are human beings agents of their own destruction as well as their own redemption? What does the novel say about the qualities and habits in both experiences in a world where "living is the hardest?" Using Cassie and Lia as examples of this speaks to what it means to be human, and a critical dynamic in the novel.
Finally, I think that a really compelling essay could be generated on the idea of friendship. Simply addressing what the novel has to say about friendship as seen in the cases of Cassie and Lia could be very profound. Lifelong friends who are separated in high school, the death of one impacts the other in such a profound way. In some respects, their friendship seems to magnify after Cassie's suicide. Being able to explore how friendship is seen in the novel could reveal much about adolescence and the concept of connection with another human being. These essay topics strike at many of the novel's themes and speak to its powerful effect on the reader.