Is This Too Much To Ask?

Obviously Carla was not the Gorgon the way Larry Talbot was the Wolfman.
Otherwise it wouldn't have mattered if Paul took her away, she would have become the Gorgon anywhere at the full moon.
Magera's spirit resided in the castle and SUMMONED Carla every full moon.
If Paul had of taken Carla from the town she would have been freed. But then Magera would have snagged another hapless female.

Wasn't it that weird off-camera music or singing that drew victims to the castle?

"Remind me to tell you about the time I looked into the heart of an artichoke."

Well- what if Megaera doesn't stay in the castle? What if she roams the countryside and turns up at people's residences, as she most assuredly did? What then?

Yeah, the days when the monsters would go door to door are long gone. Now you have to see them at their castle/lair/place of business, and half the time you need an appointment. If any one of them would go back to doing house calls, its business would skyrocket. But then, with all the chainsaws and other bulky modern equipment, I can sort of see the problem there. Also, I think monster insurance got out of hand after King Kong's disastrous weekend in the Big Apple and now they can't afford the premiums to go offsite.