Medusa was one of three sisters, the gorgons, but she was the only mortal one. Some versions say all three were born as monsters, but the predominant myths had them as gorgeous maidens. Poseidon turned her and her sisters into monsters with live snakes covering their heads. Medusa kept her beautiful face but everything else was so monstrous. And whoever dared to look into her face ended up being turned into stone.
(By some the standards of many she was irresistibly beautiful but all who dared look at her face ended up dead.)
Perseus was a Greek demi-god...one parent was human and the other was a god.
Perseus was able to get close enough to Medusa to cut off her head and kill her. He was able to approach her without turning into stone because he used his polished shield as a mirror, thus not looking directly into her face.
Hence my mom's little joke: one of the people that the United States Secret Service must protect is judged to be AWESOME by many people but in fact is a monster. Thus forcing them to wear reflective, ballistic eyewear.
Apologies for the obscure mythological reference. I will have words with my mom.