In a sense, at this stage of the novel, Madame Merle represents the complete sacrifice of individualism to society: no one has taken her independence from her, but she has chosen not to exercise it in any meaningful way. Though Isabel is very attached to her by the time she leaves Gardencourt, the reader rightly looks upon their new friendship with a sense of suspicion and disapproval.
The death of the admirable Mr. Touchett changes Isabel's life by bringing her a vast fortune. True to his desire to live vicariously through Isabel, Ralph has arranged with his father to split the money that would have otherwise all gone to Ralph between Ralph and Isabel. At this stage of the novel, this would appear to be a wonderful development for Isabel: as Ralph observes, it will preserve her independence and protect her from having to marry for money. She will be able to lead her own life, which is what Ralph most dearly wants her to do.
As the book progresses, however, the consequences of Isabel's inheritance become worse and worse, and Ralph's decision becomes more and more tragically ironic. In effect, it is Ralph's desire for Isabel to be independent that leads to Isabel's inheriting a fortune, and Isabel's wealth that prompts Madame Merle to scheme to marry Isabel to Gilbert Osmond, ruining any hope of independence that Isabel might have had.