I read this book last year and so may have forgotten much that is important. The analysis quoted by SGM all rings true.
What struck me very strongly was Lucy's ambivalent combination of admiration and contempt for many of the people around her, an ambivalence which I think is typical of a woman who is highly able, psychologically powerful, but condemned by all the socialising forces ranged against women to have very poor self-esteem.
She is scathing about herself, about her unworthiness of love; and that self-devaluation breeds a too-ready over-estimation of others. She regards other people, particularly Dr John, as being too much her superiors to have time for a worthless person like her. But at the same time she is very fully conscious of her worth despite all the self-abnegating pressures placed upon her. So she hates the people she feels compelled to admire; she is absolutely scathing of them. She knows she is better than them and she is furious with them for extracting her self-deploring admiration of them.
And, I think, she is scathing of her readers too: she taunts us by subverting our so-conventional expectations of a conventional narrative with aconventional ending.
A similar defensive hatred and contempt of the powerful those who prevent her worth from reaping its just rewards is present in Jane Eyre. But I dislike Jane Eyre because ultimately she triumphs over her oppressors by aligning herself with a powerful man, and then (courtesy of her author) symbolically castrating that man by blinding him. Lucy triumphs in the end by her own quietly determined autonomy, and her exceptional professional skills. Yes she is aided by a man -- but a man who is compelled against his rather arrogant will to love her, a man who is deferring to her power (not her feminine power over him but her autonomous worth). And he is a man who is ultimately absent: Lucy's post-novel career is as a single woman.