I see some people complaining about the "fake caveman eyebrows" of the main character, so just to clear some things up.
The way the main character is pictured matches a lot of traits that are classical in the development of schizophrenia. Withdrawal from society, lack of attention towards looks and appearance, overly complicated way of speaking (could also be a trait in schizotypal personality disorder), delusions, merging of fantasy and reality, bodily dysmorphism, etc. The list could go on. She could be a sociopath, but the delusions seem to be too strong. Borderline personality as she herself suggests in the movie is less likely, as she doesn't seem too affected by rejection.
I found that the film is quite realistic, the main character is not exaggerated at all. But that's just me.