Her Wikipedia article is here. She married twice, had two children from each marriage that survived to adulthood, was imprisoned several times, and died in exile.
The Swedish Wikimedia notes for this image, translated by Google, include this, "Gray blue dress with flower pattern in gold, narrow lower arms, wide split upper sleeves, round neckline. Tight tight white pleated collar, gold chains around the neck. Dark-faded hat with white plumage around, narrow strap under the head. Garnet of gold thread. Right hand holds in the hat, the left hand holds a white cloth. T. v. Castles of gold metal on table with red cloth. In the upper left corner, the inscription with black color: 'Margareta Wasa, Daughter of the Riksrådet, The Knight and Stand Holder Mr. Eric Johansson Wasa to Rijdboholm, Married 1: Mo with the Council and Knight Mr. Joachim Pedersson Brahe To Tärna 2: Do with Grefve Johan von der Hoija.' In the upper right corner, coat of arms with black vase against gold.” She travelled around the Baltic region extensively so I cannot guess the nationality of this dress.
From Wikimedia. The upper part of the image was obscured by a veiling reflection that was removed in the background and the inside of the hat brim with Photoshop. The upper left edge and the lower right edge were fixed with Photoshop.
This is like nothing else in this Site. It features a pleated under-garment that may also contribute the deeply flared lower sleeves. Sleeves were flared like this in the 1100s. The over-garment is a brocade and there may also be a dark under-skirt.
Keywords: 1528, Mäster Hillebrandt, Margareta Eriksdotter Vasa, Vasa family, Brahe family, von Hoya family, Countess, feathered brim hat, strap, coif, chemise, high enclosing neckline, neckline ruff, choker necklace, necklace, pendant, flared lower sleeves, bodice, trapezoidal neckline, elbow length flared puffed upper sleeves, jeweled arm bands, belt, jeweled buckle, over-skirt