One of the key aspects of Modernist literature is the use of narration to show and express the world as it is perceived by the characters themselves, including their rather bizarre thoughts and perceptions. This is known as stream-of-consciousness narration and is seen in a number of works by famous Modernists such as Virginia Woolf and James Joyce. If "Miss Brill" is analysed in a similar way, Mansfield is using exactly this technique to present to us the strange world in which Miss Brill lives, a character who the narration makes clear is able to delude herself in order to ignore the crushing loneliness that otherwise threatens to overwhelm her. Note the absurd lengths to which Miss Brill takes her perception in the following quote:
They were all on the stage. They weren't only the audience, not only looking on; they were acting. Even she had a part and came every Sunday. No doubt somebody would have noticed if she hadn't been there; she was part of the performance, after all.
The reader is allowed to see into Miss Brill's mind and her attempts to ignore her isolation and solitude. Note the way that imagining the scene as a play on a stage enables her to believe that she is noted and significant and that others care about her. Narration in Modernism seeks to expose the inner workings of characters' minds so the reader is able to see their inconsistencies and partial understanding of the world, and this is something that Mansfield achieves in the creation of this character.