The walkthroughs don't help me because they just say "show mirror to Medusa" but as soon as she appears the game takes over and she turns me to stone. How can I show her the mirror before she kills me?

Emily (fov) posted this earlier:

When you enter one of the desert screens she shows up in, turn your back immediately so you won't be looking at her when she comes in. THEN use the mirror on her. (I'm not sure exactly which screens are hers, but it seems like the ones with little snakes or reptiles on them are the ones she appears on.)