Revisiting The Sun Also Rises

I'm doing my critical essay on Brett from The Sun Also Rises. Writing it and revising has me thinking a lot about it again, so I just wanted to put my thoughts out there. 

My paper argues that Brett and Jake are both protagonists, while the war is the antagonist. 
 
At surface level, Brett does appear to be just an antagonist to Jake She seems to be a constant reminder of his war wounding, and, of course, sometimes she seems to act like a bitch.

Some critics investigate her further and discover she may have mental instabilities. Of course, that is a reasonable thought, even Jake is thought to have some instabilities due to the war. Split personality disorder, bipolar, and nymphomaniac are a few of the disorders Brett supposedly has according to critics. So I visited the DSM to check them all out. Almost all of the critics forget about Brett's time in the war and how she suffers from her ex-husband’s abuses.

Since you can't diagnose a fictional character, I have to use the phrase "Brett displays the symptoms of..." So I started looking at the text. Looking at the limited view of Brett’s history provided through Jake’s narration (which may be unreliable) it is more reasonable to think Brett displays symptoms of PTSD rather than a randomly occurring split-personality disorder. The DSM V claims that personality disorders are often a differential diagnose to PTSD (279).With Brett's history involved in the war and her abusive husband it would make more sense if she displayed symptoms of PTSD.

Thinking of Brett and Jake as having the same neurological disorder, makes it easier to see both characters as sharing the role of protagonist. Jake and Brett are both trying to figure out “how to live in it [the world] after the war altered their lives forever, rendering the war as the antagonist (SAR 152).