Having not seen this movie until now, considering the critical praise it won, I was surprised at how silly was.
Certainly, Natalie Portman conveyed ballerina Nina's every nervous tick with pained realism and she deserved her Oscar, but the plot was stupid.
Maybe I'm not up on my Odile history, but I thought the black swan was aggressive, sexual, seductive, not simply crazy as a loon. So, this whole idea of Nina literally turning into the black swan eluded me. If she had increasingly become more like Alex Forrest in Fatal Attraction that would have made more sense. Until the end when she has lost all ties to sanity, she never becomes passionate and controlling. Instead, she continues to be bascially the same trembling victim throughout, except when it comes to her mother who, alone could have caused the girl's insanity, without the help of Lily, Nina's conniving dancing rival. The mother shows us that Nina's mental fragility is probably genetic and might have occurred because of nature and the smothering nurturing she received, more than because of her demanding profession. Of course, the weight loss, lack of a social life and physical toll on Nina's body didn't help her psychological state much either.
A great example of the way Nina remained static was illuminated for me when Nina, who can never rehearse enough, observes Lily saying she doesn't need to warm up. She's always ready. 40 minutes later, when their dance director tells Nina to go warm up, I expect to hear her respond that she doesn't need to, as a sign of her transformation. Instead, she scurries off to practice. Actually, in a stalker movie like this, it is refreshing that Nina doesn't turn into a total beast. That would not only be a staple for a horror movie, but for an entertainment coming-of-age (or coming-of-stage) movie, like All About Eve. The seemingly shy novice always turns into the ruthless diva in the end.
Here, Nina isn't a diva and that doesn't change. She's dedicated and determined and though passive, she's never lacking in passion. It's not something that's hidden or concealed, ready to break out. The passion is the cause of her perennial nervousness and remote manner. She cares too much, feels too much. To expose everything inside would be like peeling away her skin -- which, not coincidentally, she does. The reserve is an inherent part of her and she can't shed this integral aspect of her psyche without damaging part of her corporal self as well. It's not like a shyness you can just grow out of. When Nina does break through it, it's because she breaks. Period.
Because we see events through Nina's eyes, it's hard to tell what happened and what didn't. For instance, I don't know if Nina actually came upon Lily having relations with their dance instructor or not. It could have been a figment of her imagination. I suppose in the end it doesn't matter. What they did is not what drove Nina over the edge. The point is, she was terrorizing herself all along and that's what led to her swan song.