The First Female Thor
Thor, the Norse god of thunder is also a Marvel Super hero. When first introduced, the lame Dr. Donald Blake found a walking stick in Norway that, when struck against the ground or a rock, became the hammer of Thor, and "Whosoever holds this hammer, if he be worthy, shall possess the power of Thor."
Soon it was revealed that Don Blake wasn't merely "worthy," but was the actual thunder god, transformed into a lame human to teach him humility by his father, Odin.
In Marvel continuity it has already been established that another human -- or even an alien; see Walt Simonson's Beta Ray Bill story arc -- may also pick up the hammer, if they be worthy, and possess the power of Thor. So now they have apparently decided to have a woman pick it up. This is the first time that a woman has become Thor ... in this continuity, that is.
But Marvel has an infinite number of continuities, a multiverse of "what if" worlds where one tiny thing changed, and in turn changes everything (see Ray Bradbury's "A Sound of Thunder" or the film The Butterfly Effect). Sometimes these worlds are explored in Marvel's regular titles, but at one time (or maybe twice) they had a comic devoted to these alternative realities, What If, and in at least one of these, a woman picked up the hammer and became Thor ... or rather, Thordis, being a Scandinavian female equivalent that she had heard.
(The female in question was Blake's nurse, Jane Foster, who was in love with him. Eventually Odin makes her give the hammer to Blake.)
So, while it's accurate to say this is the first female Thor, it isn't completely true.