The poem contains many direct allusions to the Greek myth of Medusa. For instance, line 3 ("which turned the hairs on my head to filthy snakes") and lines 18-29 ("I glanced at [...] heap of shit") refer to the most well-known aspects of Medusa: her snaky hair and her stony gaze.
In fact, allusion is so central to the poem that it isn't entirely clear whether the reader is meant to interpret the speaker as a modern Medusa herself, or just as someone who identifies with Medusa. The poem can be read either way (or both ways at once!), but the reader's choice may influence the meaning of other, more subtle allusions.
For instance, the speaker addresses the husband as her own "Greek God." This may allude to a version of the myth by the poet Ovid, in which the god Poseidon seduces (or perhaps rapes) Medusa in Athena's temple. Athena, enraged at the desecration of her temple, punishes Medusa by turning her hair into snakes. This interpretation fits in with the poem's theme of women being forced to pay for men's misdeeds: after all, Poseidon isn't punished, only Medusa is.
However, the line might also be metaphorical. The speaker may be admitting that she worshiped the husband, adored him, which makes his betrayal even worse. Perhaps it's also a little ironic: the speaker may be hinting at the husband's egotistical cruelty, as the Greek gods were known for being arrogant and capricious, punishing mortals for sport.
Near the end of the poem, the speaker looks at herself in the mirror, seeing the monster she has become. The mirror is another important part of Medusa's mythology, as looking at her with a mirror is the only way to see her without being turned to stone. In fact, Medusa is eventually defeated by the hero Perseus when he uses a mirror to sneak up on her and behead her. In this way, the mirror alludes to the mythical Medusa's downfall, and thus to the speaker's as well.