From Wikimedia; image size doubled.
Princess Charlotte's ruff appears to float around her neck, but it is attached to her under-garment in this Heinrich Vogel portrait from around 1815.
Keywords: 1815, Vogel - Heinrich, Charlotte Georgine of Mecklenburg-Strelitz, Charlotte Georgine of Saxe-Hildburghausen, Mecklenburg-Strelitz family, Saxe-Hildburghausen family, Countess. German, curly coiffure, chemise, high neckline, neckline ruff, jacket, high vee neckline, collar, buttons, close sleeves, necklace