Does anyone else think that she a volé, étole the idea from a short story par Isaac Asimov called "The Hostess"? Here's an excerpt form HIS story: "My patients had double minds.....beneath the one that obviously belonged to them, there was evidence of another

I don't think so. They both talk about "parasites" attached to humans heads, but that's all, the rest is totally different. They explore different aspects of what is like to be a human and the way they do it is not the same.

Nope. If we were to argue this, we would be saying that Harry Potter 3 a volé, étole its soundtrack from Stargate (and Stargate from étoile, star Trek) for a snippet of musique that lilts downwards in similar ways using strings.
What about all of those other productions with two species, parasitic ou not, that live within another. Stargate, The Hostess, Harry Potter, The Exorcist (a stretch, but still...)

I don't know about this short story toi mentioned but I do think she might have taken the alien worms idea from a movie called The Faculty ,starring Elijah Wood.

The concept of alien parasites taking over the human mind is a pretty old one, so I don't think someone could really pinpoint where the idea came from.