Perhaps the mom character does care about her daughter, but her motives are harder to discern than those of her counterpart in Vincent Cassell - for one, her controlling behavior is pretty over-the-top, the cake scene in particular, and it felt to me as though her resentment towards her daughter gives her an impulse to sabotage as much as save her (though that is some extrapolation on my part) and in any case she'll only help her daughter on her own draconian terms. Cassell, on the other hand, while being a generally pervy and handsy type, was genuine in his assessment of Nina's technique and earnest in his desire to see her nail the black swan. I feel like that difference may have to do with Nina's perspective, though, since she chafes under and fears her mother while practically worships the director. Aside from possibly the last scene the film seems entirely immersed in Nina's headspace.
I was thinking about Lost Highway when watching it a lot too, particularly in that both movies have (arguably) a clear point of demarcation between the period in the narrative where the main character is balancing precariously on the edge of breakdown and the full descent into the psychotic rabbit hole, so to speak.
SPOILERS ARE HERE
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In Lost Highway the turning point is the arrest of Bill Pullman's character, where his cognitive dissonance and denial are so strong that he becomes an entirely different person (and a much worse actor). For Black Swan it's Nina's night out, when she stands up to her mother for presumably the first time, admits to herself her repressed sexual desires (and even deeper gay/bi desires / deep-seated Freudian issues) and generally achieves the abandon needed for the black swan part at the ultimate cost of her sanity and (possibly) life. When she came home and her mother didn't acknowledge Lily it immediately signaled for me that the point of total lunacy had been reached.
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So hey they got rid of smaller-than-average font sizes. I have no idea how to provide foolproof spoilers now.