Her main complaint seems to be that she does not know how to safely share the inordinate amount of love she has for humanity. No doubt her suffering becomes at least partially real; she is weeping by the end of their discussion (Dostoevsky, II, 4). But the cause and focus of her suffering is her own selfishness, and though she receives some consolation and wisdom from Zossima, even his prognosis for her does not reflect much hope that her suffering will be relived, not until "you see with horror that in spite of all your efforts you are getting farther from your goal instead of nearer to it" (Dostoevsky, II, 4). Only through self-awareness, Zossima explicitly states, will her suffering be able to turn into something useful. The three women identified in these two chapters are of no real importance to the plot of the Brothers Karamazov or to the direct development of the other characters. Yet each one represents a point on the spectrum of suffering in its relation to redemption and personal growth. They are succinct examples of complex human problems, problems of selfishness, doubt, and the grinding motion of life that find their echo in the more richly defined title characters, the three brothers Karamazov. Dmitri most closely resembles this last woman; it is his selfishness that creates all of his problems, including his eventual arrest and impending imprisonment at the end of the novel -- had he not been in the money troubles he was, or even had he not flaunted the cash he received by whatever means, he would not have been suspected of his father's murder. His suffering is at every turn increased by his selfish and thoughtless actions; seeing no way out of most situations but increased selfishness -- his desire for money and/or women...

Without an acknowledgement of the suffering's cause, there can be no hope for relief, but rather it forces a spiral of continuing degradation. Ivan suffers from doubt and lack of faith; he is not selfishly turned inwards like Dmitri, but there is nothing outside of himself he believes in enough to save him. Eventually, his suffering drives him into madness. Of the brothers, it is only Alyosha whose suffering ends up leading to redemption and growth, and it is through his faith -- which he retains largely due to Elder Zossima -- that he is able to come through the suffering. There is external purpose to Alyosha's life, and suffering in that context can always be instructional and redemptive.
There are many other examples of suffering throughout the Brothers Karamazov and the rest of Dostoevsky's works, but most if not all of them follow the general principles outlined here. When suffering is a purely internal affair, springing from selfishness rather than a genuine love for something outside of oneself, then it is only destructive. This is seen in its effects on Ivan, Dmitri, and to an extent Madaem Hohlakov, as each character is consumed by their own lack of something outside of themselves on which to hinge any belief. Alyosha and the other women at Zossima's, however -- and especially Nastasya, the woman whose son had died -- have something outside of themselves to believe in; a love that is truly shared with the world. This love is both the root of their suffering and their road to redemption. Human were not meant to exist alone, and true divinity -- the real means of salvation -- do not lie within our own hearts, but in the hearts of others.