In Superman #123 (August of 1958), about a year before the real Supergirl first showed up in Action Comics #252 (May 1959), Otto Binder and Dick Sprang brought us the proto-type Girl of Steel.
This proto-type Super-Girl was brought about by Jimmy Olsen who wished her into existence by magic after being granted 3 wishes by a talking stick.
Yes, she was created by Jimmy...by rubbing a totem...at night...while wishing for a girl..just like Superman.
From the look Super-Girl is giving Jimmy I'd guess she knows all his secret fantasies. Nothing wrong with fantasies...I've got a great one starring Hayley Mills that continually runs in my brain like a picture-in-picture feature on a TV, but Jimmy has issues. Oh yeah, Jimmy is totally in love with the super-guy.
This Super-Girl is so efficient that she keeps getting in the way of Superman and creates as many problems as she solves. Apparently, Superman is incapable of doing this like looking where he is going or dialing down the power of his super-breath. So, since she is getting real annoying Super-Girl opts for self-destruction and returns to nothingness.
Superman must have learned his lesson about this because in the following year when Kara arrives he places her in an orphanage. Keeping this new Supergirl a secret from the world until she is trained in the use of her powers is a way better option than having her tearfully choose suicide.
Jimmy's second wish has to do with Superman catching criminals, and is boring. So I'll skip it.
For his third and final wish Jimmy wishes for Superman to meet his parents. In a telling Freudian slip, Jimmy accidentally writes the wish as 'mate his parents'. Superman is whisked away into the past where he assists with the romance of Jor-El and Lara. Jimmy has serious, scary issues.
After a pretty dull adventure where Jor-El saves Krypton from a mad scientist by posing as a traitor, the family-to-be says their farewells on an asteroid.
Yuck. At least Superman isn't kissing her with his eyes closed. That would be too creepy.
This issue also highlights one of the differences between the Golden and Silver Age heroes. In the Golden Age the heroes routinely killed off their adversaries. In the Silver Age it was more common for the hero to set up the bad guy, knowing they could cause their own deaths. But that was acceptable to the heroes of the time, because if they were not evil at heart they wouldn't fall for the trap and die.
The Super-Girl as a concept must have been a hit with DC because the next time she appeared it would be for semi-keeps.
I don't like like the new mall-rat maybe-evil Supergirl. My nostalgia filter and hesitation to like Loeb's writing probably has a lot to do with it. I did like the Linda Danvers/Matrix Supergirl, though. I think it will probably be a few years before the character is fleshed out enough to be more interesting. I guess I'll just have to wait and see what happens with the character.