The only information I can find about her is here. She probably has an interesting story being a Borbón from Spain who married an Argentine and died in Buenos Aires.
From antique-royals.tumblr.com; spots and flaws removed with Photoshop, particularly a series of curved lines near and including the left side of her shoulder.
The upper-puffed vs. leg-o-mutton sleeves, that extend well above the shoulder line, suggest this photo dates to ca. 1900. Her dress is decorated with striking cloth rosettes. She does not wear any jewelry.
Keywords: Maria Pia Borbón y Borbón, Maria Pia Borbón y Madan, Borbón family, Padilla y Avida family, straight coiffure, chignon, square neckline, berthe, bows, elbow length close upper puffed sleeves, cuffs, close skirt, bustle, rosettes