I believe it was a  TV movie from the late 70s or early 80s. There was a scene in which a girl was sent to another woman’s home to either pick up something or give her something. After the girl was let in (by whomI can’t remember), the woman she came to see came down the stairs and began to approach the girl. But when the woman got near the girl, she grabbed her  own throat — as if she were choking or gagging — and transformed into this horrific possessed thing. I remember thinking the transformation was scary and well done …. and that a black tongue may have been involved. Thanks ….