Read quickly, "Squire" looks like a woman tending her garden. Read again, and the details turn darker. The freshly turned soil, the dirt-stained gloves, the unmade bed and the "face flecked with gore" suggest she has killed her lover and buried him, then covered the grave with flowers. The poem never states this outright, which makes it more unsettling.
The speaker, who watches her from outside, describes her calm. She smiles in every stanza, and the repetition makes that smile feel eerie rather than warm. She is "peaceful at last," as if the act has freed her. The "so-called lover" hints at betrayal or a relationship that had gone bad, though the poem gives no further reason.
The mood is cold, controlled and darkly satisfied. Gentle images like lace, flowers and a match flame sit beside violence, and that contrast gives the poem its chill. The fire "as bright as her wit" suggests she sees herself as clever, and perhaps proud of it.