Obscure Horror Movie Scene

Hello.

I'm trying to find the name of yet another horror movie made in the late 80s or early 90s. I don't know the entire plot which is unfortunate, but here it goes: 

I believe this scene comes in at the ending of the movie. A Caucasian dude is lying down with a beautiful brunette. Possibly on a bed. It's a dark scene. I don't remember much of what is being talked about. The young woman has a female friend living with them. Currently in another room. I want to say there was a fight or argument earlier because i recall the brunetre saying something along the lines of "... stop! she's my friend" and protecting this other woman. In the current scene, while both the man and brunette woman are lying down, the woman turns away and when her face reappears it's the other lady. She looks very angry at whatever the man just said. The man of course is very surprised to see her change form. I wanna say there was something off about the woman's face like scarring or burn marks. She injures the man and sets fire to the building and that's all I can recall.