Lamia

Lamia has once been the beautiful and happy daughter of King Belus, King of Libya and the secret lover of Zeus. Lamia bears many of his children but Zeus’ wife, the jealous Hera, manages to make all of the children die (except the terrible Scylla). Lamia took revenge of having lost her own offspring by destroying the children of others and behaved in such a cruel manner that she was changed into a monster. Hera also punished Lamia by forbidding her never to sleep. In return Zeus gave her the power to remove her eyes and put them back at will.

Though perhaps more accurately:

Echidna is the mixture of a serpent and a woman, a beautiful fair-faced nymph from the waist up, but a horrible serpent below. She grew up in her cave and used her beautiful head and torso to lure men but once they were trapped, her serpent nature took over and she ate them raw.

stock images came from [link] I may toy with the background some more, but I'm not sure yet.