The Astounding She-Monster 1957

The Astounding She-Monster is a 1957 science fiction horror film starring Robert Clarke and directed, co-written and produced by Ronnie Ashcroft for Hollywood International Productions. The film focuses on a geologist, a gang which has kidnapped a rich heiress, and their encounter with a beautiful but deadly female alien who has crashed to Earth. In the UK, it was released as The Mysterious Invader. The film was released in American theaters on 1957 by American International Pictures on a double feature with Roger Corman's The Saga of the Viking Women and Their Voyage to the Waters of the Great Sea Serpent.
Gangsters Nat Burdell and Brad Conley kidnap wealthy socialite Margaret Chaffee and, joined by gun moll Esther Malone, head for the San Gabriel Mountains to await the ransom they have demanded from Chaffee's father. That night, geologist Dick Cutler sees what he thinks is a meteor crash into the forest. But he doesn't see that out of the smoke from the impact emerges a beautiful glowing blonde female extraterrestrial in a skintight leotard who can kill by touch.
The gangsters hole up at Cutler's cabin. When the alien peeks through a window, Burdell orders Conley to go after her, but the alien kills Conley, his gunshots having no effect on her whatsoever. Burdell then goes out and runs into the alien himself. Although his gunshots are also ineffective, the alien walks away backwards, allowing Burdell to retrieve Conley's body. Back at the cabin, Cutler says that Conley died of "radium poisoning" and that by carrying his body, Burdell has taken a potentially lethal dose of radium and needs to get to a doctor before he dies.
Burdell decides they should flee that night, even though they will have to navigate a dangerous mountain road in Cutler's headlight-less Jeep. But before they can leave, the alien smashes through the cabin's window. Everyone runs outside. The alien catches Malone and kills her. When the alien tries to grab Burdell, he quickly sidesteps and she tumbles down an embankment. Burdell wrongly thinks she is dead. Cutler and Chaffee have already run back to the cabin. Burdell demands that they leave at once. But as they drive off, the extraterrestrial stops them and kills Burdell.
With all the gangsters dead, Cutler and Chaffee run to the cabin again. Cutler speculates that the alien's body is made of radium and platinum, which protect her from the Earth's atmosphere. He mixes an acid solution that will kill her. When she comes into the cabin, he throws the bottle of acid at her. She is killed and disintegrates.
However, a locket she was wearing is undamaged. Cutler finds in it a note, written in English, from the "Master of the Council of Planets of the Galaxy." It is an invitation to Earth to join the Council. Cutler now realizes that the alien was a peaceful emissary who killed only in self-defense. Chaffee says that the Council, with its "superior wisdom," will surely understand that their human nature caused them to fear the etc