Is this Isabel Clara Eugenia or Catalina Micaela?
From the lost gallery’s photostream on flickr.

Isabel’s dress is similar to Infanta Catalina’s in this portrait, including the turned back sleeves. The hat and comb may be the same. She also holds the same jeweled object in her hand.
Keywords: Infanta Isabel Clara Eugenia, Princess, Habsburg family, Spanish, jeweled feathered hat, jeweled comb, high enclosing neckline, neck ruff, tabbed sleeves, hanging sleeves, lining, aglets, tabbed long tight false sleeves, cuffs, girdle, tabbed bodice, vee waistline, farthingale, aglets, carcanet necklace, necklace, earrings, clasps, rings, handkerchief, saya