How Isabel Archer becomes an object of pity : The Portrait of a Lady

As Henry James's "The Portrait of a Lady" moves inexorably toward its conclusion - the characters variously and separately heading back to England, as it appears the novel will end exactly where it began - and Isabel's life a ruin, she managing to prevent her husband from marrying his daughter off to the wealthy Lord Warburton but earning her husband's enmity in return, Isabel now having nothing, her various suitors all gone or, in Ralph's case dying, you have to look back and try to understand the point of this novel. Ultimately, it seems to me, the point is: Leave well enough alone. Isabel would have been just fine has she been left to her own devices in Albany, where she would have married well and been happy. The idea that she had to be brought to Europe to see the world and to grow in experience was the first step toward her ruin, and then the second and fatal blow was her inheritance of a small fortune. That made her an object of desire to the fortune-hunting Osmond. It's a bit of a mystery as to why she couldn't see how horrible he was and why she couldn't see through that phony, Madame Merle. But it seems her money distorted her judgment and ruined her desire for independence. It's also not clear what happened to her spirit during her years of marriage. Why is she still so subservient to Osmond? Why can't she defy him outright rather than through little devious schemes? I guess in part she worries what he will do to Pansy if she (Isabel) is out of the picture, but it's also as if she's become corrupted with the European malaise, a slave to custom, worried about appearing too brash and too bold. By the end of the novel, she is a much less vivid character, all her lines are blurred. We no longer admire her; we pity her.