It's sort of the same goddess, as in Tiamat, the Mesopotamian goddess of salt water/the sea. But her depiction as a many headed dragon was popularized by Dungeons and Dragons. She was definitely NOT a many headed dragon, or a typical western dragon at all. She might have been a large sea serpent type thing but with limbs. But it's much more likely that, like many gods, she could be a human looking person as well as a variety of creatures at will (like how Zeus transforms into eagles and swans and things).