Because you are not the admired nightingale. Because you are not the noble doe. Because you are not the picturesque ermine, armadillo, or bat.
She is trying to prove to the professor that any animal can have a poem. An animal as simple as a bat or an armadillo.
kept wearing him down after Nithad hampered and restrained him,
They kept wearing him down after Nithad had restrained him in lithe sinew-bonds.
Hear, o gods, my desperate plea To see my love beside me
Orpheus is hoping that Hades will let his loved one walk next to him again.
There he struck his lyre, and at the sound all that vast multitude were charmed to stillness The dog Cerberus relaxed his guard; the wheel of Ixion stood motionless; Sisiphus sat at rest upon his stone; Tantalus forgot his thirst; for the first time the faces of the dread goddesses, the Furies, were wet with tears. The ruler of Hades drew near to listen with his queen.
When Orpheus started to play his lyre the whole underworld stopped what they were doing. Cerberus relaxed his guard, Sisyphus stopped pushing his boulder. Tantalus forgot about his thirst. The whole underworld was just drawn to his music.
So for your arrogance and your ruthlessness I have lost the earth
Due to his arrogance, Eurydice has now not been able to return to Earth.