all her hallucinations(was that what they were?), her bloody scar, her mom clipping her nails(how are those three things related and what did they mean), why she kept imagining Mila Kunis was her enemy, all that
if anyone's reading this and hasn't seen the film yet and plans to, spoilers lie herein so Beware!
her hallucinations - idk, they're just hallucinations I guess! I mean, a lot of characters in films hallucinate, hers being because of her overwhelming desire to get the role in the first place and, eventually, fit the role perfectly after her instructor was all like 'okay you're the white swan but can you be the black swan.' I'm not even 100% sure which hallucinations in particular you're talking about, but I'm pretty sure this answer is okay.
her bloody scar - shows how the role was taking a physical toll on her. it was really just to emphasize her deterioration, I think.
her mom clipping her nails - she does peel the skin off of her nails later on if I'm remembering correctly (I honestly don't remember if this is an hallucination or not oopsies but regardless), not sure if this was something he meant to be looked at under the microscope though
all three of those things contribute in some way to how bad the role was for her, and how much it destroyed her and, of course, lead to her eventual death. especially the scar.
and she kept seeing Mila Kunis as her enemy because she was the black swan to Portman's white swan, the dark to her light, the guilty to her innocence, yada yada yada. like when she takes Portman to the club and tries to get her to pop pills (successfully I think), and Portman romanticizes her badness which manifests itself and climaxes (figuratively and literally if u kno what I mean) when she imagines them having some crazy sex. and then when Portman imagines killing Kunis, this is her transformation into the black swan, this is the turning point, this is when she lets the persona completely eclipse her actual personality and this is when she pretty much dies. there could only be one dancer who was both the black swan and the white swan in the end, and Portman let her overwhelming desire for the role completely destroy her.
I hope this clears things up a little, it's kind of disjointed and I'm a bit ill so I have no idea how clear that actually was