I had to pare down the question a bit from its original form. I think that Tagore does a very strong job of bringing out a balance of vulnerability and strength in Ratan. Indeed, there is a quest for love and security present in Ratan. The fact that the reader's introduction to Ratan is in the form of an "orphaned village- girl" who does "housework... in return for little food" brings out the fact that Ratan is alone and probably lonely. She does yearn for the belonging and the hope of solidarity that is present with the Postmaster. This is evidenced in how she appropriates his family into her own through the use of personalized pronouns:
She [Ratan] even formed affectionate imaginary pictures of them [the postmaster's family] in her mind.
The greatest evidence of her quest for belonging and her primary motivation to simply be included is most present in the asking of the postmaster to take her with him when he leaves. It is this moment that reflects both her greatest investment in her quest. Simultaneously, it is at this point where her quest suffers the greatest damage when the postmaster laughs with the dismissive, "How could I do that?" Her quest is left unfulfilled with this statement. While she experiences a type of defeat, she does not become passive and sacrifice her dignity. She draws a bath for the postmaster on his last day and then denies his money when he offers it to her as a parting gift. While she does weep for him and the loss of her quest, the embrace of her own lonely condition representative of someone "the world had abandoned," Ratan's quest is still intact in how she refuses to let him see her in an emotionally disheveled state. In the end, the reader can see that the quest for security and love was one that is not dependent on another, in a strange way. For Ratan, it was about what she loved and not necessarily what loved her back. It is here where there is some redemption present in a story where there is little to be found.