I definitely think this movie was a Full Moon/Empire feature and I remember seeing a scene from the movie on Deviantart, basically there was deadite-esque demon transforming inot a beautiful woman in a black outfit, like a silver colored bikini/swimsuit, I cannot rememember the title.

The actress I cannot remember the name of but she looks like the model/actress on the cover of Prehistoric Bimbos. I remember there was a gym scene.