This sounds like a flavor of "The Astounding She Monster" (not the film, but it had a female alien who killed with her touch). "Not of this Earth" and "Hand of Death" are interesting suggestion. Time can distort what someone remembers about a movie, and it's possible that you have mixed two of them.
I just watched ASTOUNDING SHE MONSTER last night. To know what the alien looked like would probely go a long way to solving this mystery.