Okay, in all honesty
this is a pretty lousy film! The plot is awful and contains more holes than a bowl of Swiss cheese, while the editing and pacing look pretty amateurish. And yet you don't really care about all these flaws! Supergirl is cheerful kitsch with a gorgeous lead-actress and a bunch of great stars overacting (Peter O'Toole, Faye Dunaway, Mia Farrow... ). Helen Slater is Kara, superman's niece from Krypton who goes to earth herself in order to recover the lost Omega Hedron which is a power source for the planet. The mad raving amateur witch Selena found the Omega Hedron and wants to use it to obtain world domination! Yihaa! Helen Slater looks yummy in her Supergirl outfit with miniskirt and tight top and that's about all I remembered about this film. It is never explained how exactly this Omega Hedron works
or how Kara suddenly changes into Supergirl...or even who sewed that lovely costume. This is just colorful amusement with flamboyant visual effects and attractive stars.