I've only been able to find one image of Medusa from the new Clash of the Titans. In the lone photo I used as reference for drawing this picture, her visage isn't ugly. From what I can see, apart from her hair full o' snakes and serpent's body, her face is fairly attractive. So, I can only think that she "hags-out" when turning victims to stone. I've learned her performance in the film is completely computer generated. Russian-born beauty, Natalia Vodianova was hired as the motion-capture model for the gruesome Gorgon and her attack on Perseus and his men.
The following text is from the World Book Encyclopedia Volume 13 (1976) and is copyright 2010 Field Enterprises Educational Corporation: "Medusa was one of the three Gorgons, the daughters of the sea god Phorcus in Greek mythology. She was the only mortal Gorgon. Medusa had been beautiful in her youth, and was still proud of her hair. She boasted of her beauty to Athena, who became jealous and changed her into a hideous person. Medusa and her sisters had staring eyes, protruding fangs for teeth, and writhing snakes for hair. They were so ugly that anyone who saw them turned to stone.
The following text is from the World Book Encyclopedia Volume 13 (1976) and is copyright 2010 Field Enterprises Educational Corporation: "Medusa was one of the three Gorgons, the daughters of the sea god Phorcus in Greek mythology. She was the only mortal Gorgon. Medusa had been beautiful in her youth, and was still proud of her hair. She boasted of her beauty to Athena, who became jealous and changed her into a hideous person. Medusa and her sisters had staring eyes, protruding fangs for teeth, and writhing snakes for hair. They were so ugly that anyone who saw them turned to stone.
Perseus killed Medusa by looking in his mirrorlike shield as he cut off her head. The winged horse Pegasus sprang from her beheaded body, and poisonous snakes arose from the blood that dripped from her head. Athena saved blood from Medusa's body and gave it to Asclepius, the god of healing. The blood from Medusa's left side was a fatal poison, but that from her right side had the power to revive the dead."