Dia, after quite a bit of "research" I'd have to say that it is in fact supergirl. Here is my proof. In the above picture we have Supergirl after losing half of her shirt in a battle with some villain. I guess she didn't have a blanket from krypton to make her costume.
Here she is in her short sleeve summer costume.
I believe this picture is from that lost Mardi Gras weekend.
Here she is in the 1950s, I'm not sure why her breasts are shaped like that.
I also discovered that the carpet matches the drapes, I'm sure you were wondering.