In the poem Revenge Letitia Elizbeth Landon shows us why it should.
The poem shows the speaker sweeping away someone's beloved, rubbing her happiness in her face because she had an affair with the speaker's beloved; which is a good method of evening the playing field.
The author takes away someone's lover. She conveys, "Thine own is will not be;" (Letitia, 8.2). This lets us know that the person's lover is no longer in their possession. The author also conveys, "the nights pass'd in sleepless care" (Letitia, 5.1). She has motive to bring someone pain. Letitia steals a person's lover because they brought pain upon them.
The speaker rubs her new happiness in someone's face.