{edited, added some stuff, just an informal consideration of a few of the arguments that support the accusation}

"Bella Swan is a sociopath."

It’s an extreme statement, to be sure. However, it’s not one to be dismissed offhand, without consideration towards its arguments.

First, here are a couple definitions of the term sociopath.
-Random House Dictionary:
a person, as a psychopathic personality, whose behavior is antisocial and who lacks a sense of moral responsibility or social conscience.
-American Heritage Dictionary of Cultural Literacy:
Someone whose social behavior is extremely abnormal. Sociopaths are interested only in their personal needs and desires, without concern for the effects of their behavior on others.

I'm going to discuss what seems to be the two main indicators: (1) antisocial behavior or abnormal social interaction habits and (2) thought pattern focused so extremely on the self, that negligible interest is given to anything else. Notice that neither of these are necessarily destructive or detrimental to outside society. Rather, it reflects a disturbed frame of mind and way of thinking that often leads to criminal behavior. Particularly, indicator (2) could be simplified as "egocentricity," however the word gives the false insinuation maliciousness. Keep in mind that this means that it just doesn't occur to a sociopath to think of other people outside of how they affect the sociopath themself. They may not even be able to understand how this or anything they do out of self-interest is wrong.

Part I: Is Bella antisocial?
For the time being, we are putting aside her interactions with the vampires.

Some people who are extremely sociopathic or anti-social are not concerned with appearances and openly engage in “behavior deviating sharply from the social norm” (from Meriam-Webster definition of anti-social). However, many sociopaths learn to skillfully mimic the superficial behaviors that indicate social interest in others and empathy. In this way, they are able to appear to normal to those who only see these superficial actions. Luckily, Twilight was written from Bella’s point of view, allowing us to see somewhat into her true values, concerns and intentions.

Bella certainly engages in social interaction on a daily basis in Forks. However, from before she even arrives in Forks, she has no true interest in the people around her, including her father. Her narrative makes it clear that all of her interactions and conversations were purely the result of courtesy and to hide that her true social interactions (ability/desire to bond with those near her) are abnormal. Despite many of her classmates going out of their way to welcome her warmly, Bella quickly judges everyone she meets and insults or makes fun of them. In New Moon, Bella’s entire pretense fails and she is so obviously antisocial for months that her behavior disturbs her classmates and family. However, the rest of the time she is sure to engage in the minimal amount of superficial social interaction required to appear normal.

As with her habit of calling her father “Dad” only to his face, Bella displays no actual respect for him outside of superficialities. She lies to him about her boyfriend and other things, allows Edward to sneak into his house every night, and even states she doesn’t think she needs her father’s permission to go on a long road trip alone to an unfamiliar city. Bella shows no signs of remorse or concern for these things and outwardly mimics a perfectly gracious and respectful daughter throughout.

Then she sees the Cullens. They are the only people in the town that Bella can be bothered to take an interest in. Their superficial beauty, wealth, and obvious exclusivity from the rest of society represent a social status above Bella’s own. “The isolation must be their desire; I couldn't imagine any door that wouldn't be opened by that degree of beauty.” And Edward, the available one, is her way in. Edward becomes the key to Bella’s own happiness, fulfillment and meaning in life. She quickly becomes obsessed with what he has to offer her.

Part II: Bella Lacks a Social Conscience
Exhibit A: Bella finds out a coven of vampires is in living in town. They tell her they don’t hurt people, but she has no reason to trust them. Did I mention they’re blood-sucking, people-eating-by-definition VAMPIRES? On top of that, there are bodies showing up and Bella knows the perp is a vampire. Does she try to warn or protect the entire town of very vulnerable succulent humans? No, she’s too busy trying to protect the cover story of dear Edward and his friends. Even if he kills her, she doesn’t want anyone to know it was him. She has no concern for the fact that she would be making it easier for him to prey on other people in the town because her feelings for Edward make him more important than anything in the world, even if he turns out to be a BLOOD-THIRSTY MASS MURDERER.

Exhibit B: Bella wants to be a vampire. She has no reservations about this. She wants that increase in status no matter how it affects other people. She is told that newborns begin with extreme bloodlust, that she would be overcome with the desire/need to kill people and eat them. Edward says he will protect her from hurting anyone, but she is told that newborns are extremely strong as well. It’s not difficult to imagine Edward being over-powered. However likely or unlikely it is, there exists the possibility that Bella becoming a vampire could result in the deaths of innocents. She does not even consider for a moment the risk she is taking with other people’s lives. What. The. Hell? That takes a HUGE lack of social conscience and empathy.


Conclusion:
I’m not formally trained to make a diagnosis, but it seems clear to me that Bella has sociopathic tendencies or is severely abnormal in some way. Or maybe I'm just desperate to believe that there is no way a sane human could think the way Bella does.

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