From the Classical Ages toward the main story of Medusa took its form. She was, as described in the article's introduction, a hideous monster with snake hair, that turned men into stone until she was slain by Perseus.
There are no stories that tell us of Medusa turning people to stone, nor any tales of her harassing or killing people (unlike other Greek monsters such as Scylla and Charybdis). Although she had the power to kill, she was not inherently evil.