There is little genealogical information about her; her almost microscopic article in thepeerage is here. Her mother was Elizabeth Howard who was the daughter of Charles Howard and Catherine Carey. Catherine Carey’s parents were Anne Morgan and Henry Carey, son of Mary Boleyn and, possibly, Henry VIII.
From Bonhams Web site; fixed the left, upper, and right edges and removed spots from the background with Photoshop. Also posted to the Transition from Ruffs to Collars - 1620 to 1630 Album here.
This shows a farthingale with bilobite ruff and wide collar with possible blonde lace. The full under- (false) sleeves are divided by arm bands.
Keywords: Johnson, Margaret Stuart, Margaret Stewart, Margaret Mennes, curly coiffure, braided chignon, earrings, necklace, over-bodice, lace-edged modesty piece, vee décolletage, rosettes, neckline ruff, fitted bodice, scoop décolletage, draped jewed bodice ornament, tabbed false sleeves, full virago under-sleeves, jeweled arm bands, waist band, vee waistline, close skirt, farthingale