The poem is a single quiet moment. It is the morning of the speaker's birthday, just days after the first Passover Seder held without "her" at the table. The poem never says who she is, but the way her absence hangs over the holiday suggests someone close, perhaps a person who has died or is otherwise gone. That is an inference from the text, not something the poem states.
Then comes the image at the center: she raises a "narrow-ruled hand" to the sky and exhales. The odd phrase makes the hand sound like lined notebook paper, which could point to writing, record-keeping, or a memory of her. The title, "Stellar," and the sky she reaches toward hint at stars, and perhaps at a lost loved one imagined above. The mood is hushed and tender. Grief and celebration sit side by side, and the exhale feels like both a release and a held-in sigh.