The postillion was struck by lightning

You're braver than I. So, I take it back, Austrian and Spanish both.

Exhibit 1 for the prosecution: Mary of Spain, who married the Holy Roman Emperor. Note the inbred Habsburg slack jaw and look of stupidity on page 33 of Moda a Firenze (can't find it online, alas):

http://upload.wikimedia.org/wikipedia/commons/2/27/Giuseppe_Arcimboldi_003.jpg

and
http://upload.wikimedia.org/wikipedia/commons/b/bc/Maria_of_Spain_1557.jpg

She was the mother of two remarkably pretty girls (SIXTEEN CHILDREN!), Anne of Austria (who married Philip of Spain) and Elisabeth of Austria, Queen of France.

Joanna herself, seems to have the consistent expression of OMG, don't laugh at my hair. She, however, was unhappily married to that brute, Cosimo II.

http://www.theflorentine.net/articles/article-view.asp?issuetocId=3896
can't find a color version. It is in Moda a Firenze, and the gold embroidery on her ropa and kirtle matches the gold of her hair.

http://upload.wikimedia.org/wikipedia/commons/9/94/Giuseppe_Arcimboldi_005.jpg

This is Joanna's sister, Katherine, who became the Queen of Poland and Duchess of Lithuania:

http://upload.wikimedia.org/wikipedia/commons/b/be/KatarzynaHabs.jpg

and another sister, Barbara, who became the Duchess of Ferrara.

http://upload.wikimedia.org/wikipedia/commons/3/39/Francesco_Terzio_005.jpg

And as a side note, this is interesting:

http://www.guide2womenleaders.com/womeninpower/Womeninpower1540.htm