Nikky's poem is about a love that did the opposite of what it promised. The speaker says she fell "madly" for a boy, and that he told her he would fix her. That promise suggests she already felt damaged when they met, and that she hoped he would be the one to heal her. Instead, he made things worse.
The most striking part is the way the lines break apart on the page. "Smaller / And smaller / And smaller" shrinks the poem just as the speaker's pieces shrink, so we see the damage as well as hear it. The trailing dots at the ends of lines leave things hanging, as if she can't quite finish the thought, or as if the pain lingers.
The mood is raw, tired, and sad. There's hurt here, and maybe a little disbelief at how far trust can be betrayed, but there is no anger shouted out loud. The final word, "unfixable," feels close to despair, though "almost" leaves a very small opening.