Snake Princess

Suggestions:

Night of the Axe Horror Maniacs: I Want to See Pigblood! The Pineland Murders! Panic in the Forest Roots of Evil

Lovebirds (love snakes?) Bunga the Snake Princess and Sanca the python live in a forest and transform into humans and hold erotic dance ceremonies every full moon. Some explorers stumble upon them and Sanca is accidentally shot. This incident makes Bunga sad, angry and vengeful and she begins killing everyone off.