I think that this is where Mansfield's story truly takes a sense of flight from being very good to being downright great. To fully answer the question, we might have go back a bit and set up what is happening. Go to the park. Miss Brill is engaging in her usual Sunday afternoon practice, presuming that the entire world is present and is for her and her alone. The two lovers sit down at the bench and begin to ridicule her and she recognizes it for what it is. At that moment, the answer to your question is present. Her reaction is not noted, yet given that she had to hear it, I think that we can begin to grasp that she does come to a realization. It is not stated directly, but I tend to think that it is implied to a certain extent. It might not cause her to stand up, demand that she conceive a new life of herself out of the deceit from self, and embrace a "truth- seeking" vision of consciousness. Yet, it does force to admit, even in the smallest portion, that the vision of her self and her world that she had created does not fully mirror reality. This would be why she leaves the park, as she does have a perception that there is a chasm between both, and hence, the realization. Yet, at the end, when she blames the stole in putting in the box and hears "something crying," I think it might be representative of a couple of things. One might be that she manages to suppress the harsh truth about the difference in her perception of herself and reality and her state of being in it. The other might be that she does suppress whatever small realization is there in blaming the stole. I think that this is where the reader is able to take what they can from the text to prove their point. In my mind, it's this ambiguity and this sense of ambivalence that is hauntingly powerful in Mansfield's work.