From Wikimedia; removed spots and flaws with Photoshop. One long vertical flaw was removed except where it passes through her ruff and the stripes of her skirt. Also posted to her Subalbum here.
All parts of her dress appear to be made of the same material covered by a black surcote with tabbed false sleeves.
Keywords: Infanta Isabel Clara Eugenia, Isabel Clara Eugenia de Austria, Infanta de España, archiduquesa de Austria, soberana de los Países Bajos y de Borgoña, Princess, Spanish, Habsburg family, curly coiffure, jeweled framing feathered headdress, earrings, lace edged wide neckline ruff, high enclosing neckline, fitted basque bodice, jeweled pendant, long tapered false sleeves, lace-edged ruffled cuffs, surcote, tabbed hanging sleeves, girdle, peplum, basque waistline, full skirt, fan, saya