How bad is it? It's a very standard low budget science fiction film.
Should you see it? No.
This was produced by Roger Corman, reuses footage from his "Battle Beyond the Stars" and reuses the plot from his "Not of This Earth." A female alien takes on a human body, needs blood from others to live (making this a vampire film) and kills with death ray eyes. She starts becoming more and more human and falls in love with a doctor who tries to cure her, just as other aliens arrive to eliminate her. There's some laughs in the alien's learning to speak English and some adequate nude scenes, but not enough to make this something to watch.