I think her "illness" could be a variety of things. First off, due to her previously extravagant lifestyle, it is highly likely that her attitude towards the circumstances of her new lifestyle result is a classic case of narcissism. The character of Jasmine is very conceited and materialistic; she also enjoys talking about herself to anyone around who will listen. On the contrary, she is highly insecure and unsure of herself which might be causing her over-the-top self-centeredness. In addition to this, my impression during the movie (which was great, by the way) was that she was also suffering from a type of culture shock. Her new situation is radically different from the comfortable situation in which she previously lived, and her attitude that everything around her is "distasteful" and unworthy of her attention suggests that she is simply just not acclimated to her surroundings. This also might be a defense mechanism, as her vulnerability in these unfamiliar waters is glaring.