My original tumblr post was here. This is the November 1942 edition of Fantastic Adventures. The cover was done by H.W. McCauley. It was first posted on Tumblr by Good Girl Art and comes to us via inkycurves. The ISFDB has an entry for the issue here and also provides us with a cleaner version of the cover.
I like the projection on the top of her belt that protects her navel from stray laser bursts.