This movie must have been an Empire/Full Moon feature but I remember seeing a scene from it on Deviantart in which a deadite-esque demon turns into a blonde model in a black outfit, I definitely think it was a bikini or swimsuit, I don’t remember the movie’s title but it was on Youtube.
I don’t think it was Night of The Demons but I definitely think it was kind of similar to that, the outfit was definitely a black swimsuit and it was a blonde actress (not Linnea Quigley although similar kind of hair style to her character), she looked kind of wicked witch-like as a demon with a deadite look. The Deviantart account I saw this on is Juliegrey 2001
I might have found it in this folder:
https://web.archive.org/web/20230106085845/https://www.deviantart.com/juliegrey2001/gallery/61017186/transforming
And also this founder https://web.archive.org/web/20230106085845/https://www.deviantart.com/juliegrey2001/gallery/58783927/random-shots-of-transformations