The speaker describes an imaginary friend who sounds less like a playmate and more like an anxious double. She cries, wrings her hands, hides under the table, and tells stories about terrible things that have happened or might happen. Her habits are rigid: fussy about fingernails and socks, strict about bedtime and sunrise. The odd line about never having time for anything important, yet never doing anything trivial, suggests a life squeezed into worry and routine.
The speaker's tone is tired and a little tender. "The poor thing" sounds both sympathetic and exasperated. The speaker tries to coax her outside but can't shake her, since she "follows and precedes" them everywhere. That small phrase hints she may be part of the speaker, even ahead of them.
The ending turns the poem around. The friend asks, "Who is imaginary?" and "Are you sure you are real?" The mood shifts from gentle humor to unease, leaving us wondering whether this fearful figure is the speaker's own hidden self.