Her article in thepeerage is here. She was the daughter of Anne Clifford.
Lady Margaret's chemise appears to be made to match her bodice sewn to it in this 1632 van Dyck. This style would not change much for about 50 years.
Keywords: 1632, van Dyck, Glembin, Margaret Tufton, Cecil family, Tufton family, Bitish, curly coiffure, proto-hurluberlu coiffure, jeweled headdress, bun, chemise, elbow length under-sleeves, bodice, trapezoidal décolletage, elbow length puffed sleeves, slashed sleeves, girdle, natural high waistline, necklace, earrings, brooch, jeweled bodice, clasps, jeweled skirt ornament